DE212022000095U1 - image projection - Google Patents

Abstract

Diffractive structure arranged to spatially modulate light that can be converted into an image by a viewing system, the diffractive structure being configured to direct light into a plurality of hologram channels, each hologram channel being a different part corresponds to the picture.

Description

AREA

The present disclosure relates to image projection. More specifically, the present disclosure relates to a diffractive structure for determining a diffractive structure, such as. B. a hologram or a kinoform. Some embodiments relate to real-time calculation of holograms based on eye-tracking information. Some embodiments relate to projection of virtual images. Other embodiments relate to the projection of a real image. Some embodiments relate to viewing a projected image through a waveguide. Some embodiments relate to an alternator, such as. B. an imaging unit. Some embodiments relate to a head-up display.

BACKGROUND AND INTRODUCTION

Light scattered by an object contains both amplitude and phase information. This amplitude and phase information can e.g. B. can be captured on a photosensitive plate by known interference techniques to form a holographic record or "hologram" containing interference fringes. The hologram can be reconstructed by illuminating it with appropriate light to produce a two-dimensional or three-dimensional holographic reconstruction or display image that represents the original object.

With computer-generated holography, the interference process can be simulated numerically. A computer generated hologram can be computed using a technique based on a mathematical transform such as a Fresnel or Fourier transform. These types of holograms may be referred to as Fresnel/Fourier transform holograms or simply Fresnel/Fourier holograms. A Fourier hologram can be viewed as a representation of the object in the Fourier domain and in the plane, or as a representation of the object in the frequency domain and in the plane. A computer generated hologram can e.g. B. also be calculated by coherent ray tracing or a point cloud technique.

A computer generated hologram can be encoded on a spatial light modulator arranged to modulate the amplitude and/or phase of the incident light. The light modulation can, for. B. with electrically addressable liquid crystals, optically addressable liquid crystals or micromirrors.

A spatial light modulator typically includes a multiplicity of individually addressable pixels, which may also be referred to as cells or elements. The light modulation scheme can be binary, multilevel or continuous. Alternatively, the device can be continuous (i.e. not made up of pixels) and the light modulation can therefore be continuous across the device. The spatial light modulator can be reflective, i. that is, the modulated light is output by reflection. The spatial light modulator can also be transmissive, meaning that the modulated light is output in transmission.

A holographic projector can be provided with the system described here. Such projectors are used, for example, in head-up displays (HUD) and LIDAR (Light Detection and Ranging).

SUMMARY

Aspects of the present disclosure are defined in the appended independent claims.

The present disclosure and drawings generally show one-dimensional cases to facilitate explanation and illustration. However, those skilled in the optical arts will understand that the concepts described and shown can extend to two dimensions to create two-dimensional images from two-dimensional holograms. For example, while only one-dimensional pupillary dilation is described and shown, the reader should understand that the present disclosure extends to two-dimensional pupillary dilation - e.g. B. using two one-dimensional pupil dilators in series.

The present disclosure relates to image projection. It also relates to an image projection method and an image projector comprising a display device. The present disclosure also relates to a projection system including the image projector and a viewing system. The present disclosure is equally applicable to a monocular and binocular viewing system. The viewing system may include an eye or eyes of the viewer. The viewing system includes an optical element with optical power (e.g., human eye lens(es)) and a viewing plane (e.g., the retina of the human eye(s)). The projector can be referred to as an "alternator". The display device and the image produced (or perceived) by the display device are spatially separated from one another. The image is generated or perceived by a viewer on a display plane. In some embodiments, the image is a virtual image and the display plane may be referred to as a virtual image plane. The image is created by illuminating a diffractive pattern (e.g., a hologram) that is displayed on the display device. The present disclosure further relates to providing (e.g., computing) a diffractive pattern for image projection and to the diffractive pattern.

The display device includes pixels. The pixels of the display device bend the light. According to known optics, the size of the maximum diffraction angle is determined by the size of the pixels (and other factors such as the wavelength of the light).

In certain embodiments, the display device is a spatial light modulator, e.g. B. a spatial light modulator (SLM) with liquid crystals on silicon (“LCOS”). The light propagates through a range of diffraction angles (e.g., from zero to maximum diffraction angle) from the LCOS to a viewing device/system such as a camera or an eye. In some embodiments, augmentation techniques may be employed to increase the range of available diffraction angles beyond the conventional maximum diffraction angle of an LCOS.

In some cases the image is a real image. In other embodiments, the image is a virtual image seen by a human eye (or eyes). The projection system or light engine can be configured so that the viewer looks directly at the display device. In such cases, the light coded with the hologram is transmitted directly to the eye or eyes. This light can be referred to as "spatially modulated" or "holographic light". In such cases there is no intermediary holographic reconstruction, either in free space or on a screen or other photosensitive surface, between the display device and the viewer. In such embodiments, the pupil of the eye can be considered the entrance aperture of the viewing system and the retina of the eye can be considered the viewing plane of the viewing system. It is sometimes said that in this configuration the lens of the eye performs a hologram-to-image conversion.

In accordance with principles of known optics, the range of angles of light emanating from a display device or viewing window that can be seen by an eye or other viewer/system varies with the distance between the display device and the viewer. For example, at a viewing distance of 1 meter, only a small angular range of an LCOS can propagate through the pupil of the eye to form an image on the retina at a given eye position. The angular range of light rays emanating from the display device that can successfully penetrate the pupil of the eye to form an image on the retina at a given eye position determines the portion of the image that is "visible" to the viewer. In other words, not all parts of the image are visible from any point on the viewing plane (e.g. from any eye position within a viewing window such as an eye-motion box).

In some embodiments, the image perceived by the viewer is a virtual image appearing in front of the display device, i. H. the viewer perceives the image as being further away from him than the display device. It is conceptually possible to view a large number of different virtual pixels of a virtual image. The distance between a virtual point and the viewer is referred to here as the virtual image distance for this virtual pixel. Different virtual points can of course also have different virtual image distances. Individual light rays within bundles of rays that are assigned to each virtual point can each take different optical paths to the viewer via the display device. However, only some parts of the display device and thus only some of the rays from one or more virtual points of a virtual image may be in the user's field of view. In other words, only part of the light rays from some of the virtual points of the virtual image reach the user's eye or eyes via the display device and are thus visible to the viewer. So, conceptually, the viewer is looking at a virtual image through a "display device-sized window" which can be very small, e.g. 1 cm in diameter and at a relatively large distance, e.g. B. 1 meter. And the user sees the display device-sized window through the pupil(s) of his eye, which can also be very small. Accordingly, the field of view becomes small and the specific range of angles that can be seen is highly dependent on the particular eye position.

It is often desirable for an optical system to be physically small - for example, when deployed in a location where space is at a premium and/or real estate value is high. However, physical limitations are usually associated with functional limitations. For example, with traditional optical systems, the use of a small display device usually comes with a limited field of view (FOV), which limits the visibility of the images. The present disclosure addresses the technical problem of how to increase the field of view - ie how to increase the range of angles of light rays that propagate from the display device and that can successfully pass through the pupil of an eye to form an image generate - when the display device is small (relatively speaking) and the projection distance is (relatively speaking) large. In some embodiments, the projection distance is at least one - e.g. B. at least two orders of magnitude larger than the diameter or width of the aperture of the display device (ie the size of the pixel array). More specifically, the present disclosure addresses the technical problem of how to do this with what is known as direct view holography, in which a hologram of an image is presented to the human eye and not the image itself The light received by the viewer is "holographic light" that has been spatially modulated according to a hologram of the image.

Pupillary dilation is used to increase the field of view, thereby increasing the maximum propagation distance over which the full diffraction angle of the display device can be used. The use of a waveguide can also increase the user's lateral eye space, allowing some movement of the eye(s) while still allowing the user to see the image. In some embodiments, the pupil dilation is a waveguide pupil dilation. The present disclosure relates generally (but not exclusively) to non-infinite virtual image distances; H. to virtual images at close range.

The present inventors have established that so-called “ghost images” occur in conventional holography for a non-infinite virtual image distance—that is, for virtual near-field images. This can be caused by the different possible light propagation paths through the waveguide. A ghost image is a lower intensity replica of a main image. The main image with the highest intensity can be referred to as the primary image. Each ghost image can be referred to as a secondary image. The presence of ghost images can significantly degrade the quality of a perceived virtual image. The ghosting can give the impression that the main image is blurry.

Aspects of the present disclosure relate to various approaches to solving problems caused by ghosting. Some of the solutions disclosed here have proven successful in removing or preventing ghosting. Some solutions disclosed herein have been shown to modify/manipulate the sprite to enhance or enhance the primary/non-sprite.

In accordance with aspects of the present disclosure, an alternator is arranged to provide spatially modulated light to a viewing system having an entrance pupil. The display system includes a display device arranged to display a hologram and spatially modulate light in accordance with the hologram. The display system further includes a hologram engine arranged to output a hologram for display on the display device to enable the viewing system to see or perceive an image of a target image or object at a particular location. A pupil dilator is provided which can be positioned with respect to the display device to ensure that the viewing system receives light that corresponds to the entire image (i.e. to provide the maximum field of view) without having to change the position of the entrance pupil.

A method for determining a diffractive structure of an image for a system comprising a display device and a viewing system is disclosed herein. The diffractive structure can be a hologram, and the term "hologram" is used below only as an example for a diffractive structure according to this disclosure. The diffractive structure can be a complex hologram, a pure phase hologram, or a kinoform. The display device is arranged to display the hologram. The viewing system is arranged so that the hologram is viewed through a dilated pupil. The pupil expander provides a variety of light propagation paths from the display device to the viewing system.

According to aspects of the present disclosure, there is provided (e.g., computed) a hologram that includes a display device on which the hologram is displayed causes channels of spatially modulated light to be output under appropriate lighting. In at least some arrangements, each channel corresponds to a respective contiguous area of the image represented by the hologram. Each channel can correspond to a different contiguous part or area of the image, so that together the channels result in a holographic light of the entire image. A pupil dilator may be provided between the display device and a viewing system, arranged to direct each channel to an input aperture of the viewing system. It can be assumed that each channel has a unique central axis that defines a primary (or "core") direction of movement of that channel with respect to the display device, for example with respect to a central point or other reference point on a light-emitting surface of the display device. The reader will therefore understand that each channel may be characterized by an axis which may be considered the channel's optical or propagation axis. Each axis may be characterized by a unique angle with respect to the normal of the display device. Each axis may be a straight line connecting the center of the display (or hologram) to the center of the illuminated area or light pattern of the channel (ie, the center of the cross-sectional area of the light channel).

The cross-sectional area of one or more of the channels may be of a size and/or shape corresponding to the size and/or shape of the entrance aperture of the viewing system. For example, if the entry port is a human eye, the channels may have a substantially elliptical or oval cross-section. In embodiments involving hologram calculations, the calculation process may include clipping or cropping the hologram according to the size and/or shape of the entrance aperture and/or according to the size and/or shape of the display device.

In some cases there is no overlap between the channels in terms of image content. In other embodiments, the channels overlap in terms of image content. This overlap is partial and relatively small. For example, two adjacent channels may both contain information about the same part of the picture. So it can be said that the channels can partially overlap - in terms of image content / solid angles in the field of view.

It is possible to characterize channels in terms of angles in the field of view. These angles can be measured from the normal of the display device/hologram. Each channel can be characterized by two angles - for example a first angle on an xz plane and a second angle on a yz plane, where the z direction is perpendicular to the display device/hologram and represents the general direction of light propagation from the hologram. The x-direction can be horizontal and the y-direction can be vertical. For example, in the x-direction (horizontal field of view), a first channel can correspond to the angle range 0 to +4 degrees and a second angle to the range +3 to +7 degrees. In this example there is a 1 degree overlap. In this example, both the first channel and the second channel contain information about the angular content of the image, or the angles of the horizontal field of view, ranging from +3 to +4 degrees. Of course, both channels contain additional information. The overlap is relatively small - for example no more than 25% of the angular range allocated to each channel, e.g. B. not more than 10%.

In some embodiments, the size of the entire angular range (not just the intersecting angular range) associated with each channel is the same. In other embodiments, the size of the angular range associated with one angular channel is different than another.

There is disclosed herein a method of computing a hologram of an image, the method comprising at least one step including cropping in accordance with the entrance pupil of the viewing system to form a hologram which, when illuminated, forms spatially modulated light , where continuous light channels of the spatially modulated light correspond to continuous regions of the image. A continuous light channel can be defined by a continuous range of light beam angles of the spatially modulated light. All pixels of the hologram contribute to each channel, so light rays contributing to each channel can be emitted from several different pixels of the display device on which the hologram is displayed and illuminated. These light rays combine into a continuous channel, each channel having a unique respective primary direction of propagation relative to the display device. For each channel a core or an axis in the direction of propagation can be defined. For each individual hologram pixel, the light of the different channels is emitted from this pixel at different angles.

Each continuous light channel of spatially modulated light corresponds to a corresponding continuous region of the image. The spatially modulated light can be divided into any number of continuous light channels. In some embodiments, the light channels are non-overlapping. In other embodiments - e.g. e.g. those additionally including an optical combiner with optical power (e.g. a vehicle windscreen) between the waveguide and the viewer - some light channels may at least partially overlap. The method disclosed herein defines a diffractive structure arranged to spatially modulate light that can be converted into an image by a viewing system, the diffractive structure being configured to direct light into a plurality of hologram channels, where each hologram channel corresponds to a different part of the image.

For clarification, the image produced or perceived by the viewer is a holographic reconstruction of a target image. The holographic reconstruction is formed from a hologram based on the target image. In some embodiments, the hologram is determined (e.g., calculated) from the target image.

The hologram can be calculated using any suitable technique. Several possible hologram calculation techniques are disclosed here, but the present disclosure is not limited to the examples given. In some embodiments, the hologram may be modeled using a modeling technique, e.g. B. a ray tracing technique, such as a so-called "point cloud" hologram computation technique. In such embodiments, the hologram engine may be configured to receive contribution information identifying contributing and non-contributing areas of the display device based on the position of the entrance pupil. The contributing areas of the display essentially propagate the light that passes through the entrance pupil at the particular location. The non-contributing areas of the display essentially spread the light stopped by the entrance pupil at the particular location. The contribution information also identifies (i) at least one primary contributing area of the display device that propagates light to the viewing system and contributes to a primary image, and (ii) at least one secondary contributing area of the display device that propagates light to the viewing system and contributes to a secondary image . The hologram engine is further configured to determine a hologram based on the at least one primary contributing area of the display identified by the processing engine. The hologram engine is further arranged to output the hologram to the display device for display.

By identifying contributing and non-contributing areas of the display, the lighting device can determine which part or parts of the display can usefully be encoded by the hologram to positively contribute to the formation of the primary image, for a particular position of the entrance aperture of the viewing system. This can, for example, correspond to the position of the viewer's eye at a certain point in time. In addition, the illumination system can determine which parts of the display device cannot transmit light through the entrance aperture and therefore should not be filled with hologram values. In addition, the lighting program can distinguish between parts of the display device that contribute positively to a "main" target image and parts that contribute to a copy/replica or "ghost" version of the main image. In this way, the hologram can be omitted in so-called secondary areas in order to eliminate the ghost images.

A further improvement is that the hologram displayed in an additional area can be determined based on a shifted or changed position of a pixel (ie a point within a desired image to be holographically reconstructed). This changed position may be referred to as a "secondary pixel", but that is shorthand for saying that it is a secondary (ie changed) position of the (primary) pixel. In short, a modeled/calculated position of a pixel can be changed (e.g., shifted on an image plane) such that light propagating from the changed position over the additional area on the display device arrives at a desired position on a viewing plane to effectively boost the primary image. Therefore, in this alternative approach, the hologram for the additional contributing area is determined based on a different position of the pixel than that used to identify a primary contributing area on the display device. The optical path length from the primary pixel typically differs from the optical path length from the secondary pixel to the corresponding image created at the viewing plane. Thus, the hologram determination process can be said to be a shift or ver shifting the pixel used in the hologram determination process.

In this way, an intelligent and efficient lighting system is provided that can be configured and operated to provide sharp, accurate images corresponding to holograms that have been determined in a rational and computationally efficient manner.

A method of determining a hologram for display on a display device is disclosed. The method includes determining the location of the entrance pupil of a viewing system arranged to view the hologram and identifying contributing areas and non-contributing areas of the display device, wherein the contributing areas of the display device substantially propagate light passing through the entrance pupil of the viewing system at the particular location, and non-contributing portions of the display substantially propagate light that is stopped by the entrance pupil of the viewing system at the particular location. The method further comprises identifying at least one primary contributing area of the display device that provides light that contributes to a primary image and at least one secondary contributing area of the display device that provides light that contributes to a secondary image; and determining the hologram based on the at least one primary contributing area of the display device.

There is provided a diffractive structure arranged to spatially modulate light that can be converted into a target image by a viewing system, the diffractive structure configured to produce a plurality of discrete light patterns, each light pattern corresponds to another part of the target image, the shape of each discrete light pattern substantially corresponding to the shape of an entrance aperture of the viewing system.

There is provided a diffractive structure arranged to spatially modulate light that can be converted into an image by a viewing system (comprising a lens), the diffractive structure arranged to separate light into a plurality of discrete light channels, each light channel having a cross-sectional shape that substantially corresponds to an entrance pupil of the viewing system, and each light channel substantially corresponding to a different part of the image.

A method of determining a hologram for display on a display device and forming a virtual image perceptible from a viewing plane by viewing a hologram displayed on the display device through a waveguide is disclosed. The method includes, for each virtual pixel of the virtual image, determining the coordinates of the virtual pixel, [ _xvirtual , _yvirtual , _zvirtual ], determining a viewing position in the viewing plane, and determining a number of light reflections, B, within the waveguide associated with a primary image formed by the waveguide are connected. The method further includes ray tracing from the virtual pixel to the viewing plane for "B" light reflections within the waveguide and determining the coordinates [x _LCOS (B), y _LCOS (B)] of a principal light ray at the display device for the light propagation of [ _xvirtual , _yvirtual , _zvirtual ] to the viewing plane with B reflections. The method further includes determining active pixels of the display device within an area defined by [x _LCOS (B), y _LCOS (B)]; and determining a partial hologram comprising an amplitude and/or phase hologram component for the active pixels by propagating a lightwave from [ _xvirtual , _yvirtual , _zvirtual ] to the active pixels.

The chief ray may be a ray of light determined (e.g., calculated or modeled) to travel from the virtual pixel across the display device to a primary or "main" pixel of the virtual pixel on the viewing plane.

The disclosed method may further include combining the partial holograms - each calculated for two or more corresponding virtual pixels - to form a hologram.

The method may further include determining a position of the main image of the virtual pixel in the viewing plane [ _xsensor , _ysensor ].

The method may further include, for each DB value allowed by the waveguide, ray tracing from [ _xsensor , _ysensor ] to a virtual image plane _zvirtual for B+DB reflections and determining virtual point coordinates, [ _xvirtual (DB), _yvirtual (DB ), _zvirtual ], which are mapped to [ _xsensor , _ysensor ] for B+DB reflections. The method may further include determining the coordinates [x _LCOS (B+ΔB), y _LCOS (B+ΔB)] of a principal ray at the display device for light propagation from [ _xvirtual (DB), _yvirtual (DB), _zvirtual ] to the viewing plane with B+DB reflections and the identification of additional active pixels of the display device within a second region (ie, (ie a additional area) defined by [x _LCOS (B+ΔB), y _LCOS (B+ΔB)]. The method may further include determining an additional sub-hologram comprising an amplitude and/or phase hologram component for the additional active pixels by propagating a lightwave from [ _xvirtual (DB), _yvirtual (DB), _zvirtual ] to the additional active pixels .

According to some disclosed embodiments, the hologram can be calculated by determining complex light fields, where the method can be iterative. According to one embodiment, the method comprises a first to fifth stage. The first stage involves determining a first complex light field at an entrance pupil of the viewing system. The first complex field of light results from the propagation of light from a display plane of the display device along at least one light propagation path of the pupil dilator. The first stage also includes cropping in accordance with the entrance pupil of the viewing system. The second stage includes the determination of a second complex light field in a sensor plane of a sensor of the viewing system. The second complex light field results from propagating the light of the first complex light field from the entrance pupil through a lens of the viewing system. The second stage also involves modifying the amplitude component in accordance with the image. The third stage involves the determination of a third complex light field at the entrance pupil. The third complex light field results from the backward propagation of the light of the second complex light field from the sensor plane back through the lens. The third stage also includes cropping in accordance with the entrance pupil. The fourth stage involves determining a fourth complex light field in the display plane. The fourth complex light field results from propagating the light of the third complex light field back along the at least one light propagation of the pupil dilator. The fourth stage also includes cropping in accordance with the display device. The hologram is extracted from the fourth data set. The first to fourth steps can be repeated iteratively. The hologram is converging and likely improving with each iteration, but will plateau. The process may terminate when the hologram extracted from the fourth stage is of acceptable quality, or the rate of change at each iteration is below a threshold, or an allotted time has elapsed. To clarify, the extracted hologram is the hologram for display on the display device.

The term "backward propagation" is only used to indicate that the direction of propagation of the light in the third and fourth stages is different or substantially opposite to that in the first and second stages. In this regard, the propagation of light in the first and second stages can be referred to as "forward propagation". In some embodiments, "forward propagation" and "backward propagation" are mathematically inverses of each other.

The term "pruning" is used here to mean a process of selectively discarding information, such as B. light field information, outside an area or region of interest, such. B. outside of a light aperture. In some embodiments, “clipping” is a data processing step that includes discarding data points, zeroing data points, or simply ignoring data points outside of the aperture.

Here reference is made to a "complex field of light". The term "light field" simply denotes a light pattern with a finite size in at least two orthogonal spatial directions, x and y. The word "complex" is used here only to indicate that the light at any point in the light field can be defined by an amplitude value and a phase value and can therefore be represented by a complex number or pair of values. For the purposes of hologram computation, the complex light field can be a two-dimensional array of complex numbers, where the complex numbers define the light intensity and phase at a plurality of discrete locations within the light field. According to the method disclosed here, the complex light field is propagated back and forth between a hologram plane and an image plane in the +z and -z directions. Light propagation can be simulated or modeled using any number of different approaches or mathematical transformations known to those skilled in the art of wave optics.

The disclosed method is designed to determine a hologram for a relatively small display device and project it over a relatively large distance, where the hologram is projected directly onto the viewing system(s) and the method can be performed in real time. The relatively small size of the display device and the relatively large projection distance may necessitate a pupil dilator. The disclosed method also addresses the optical complications that arise from the use of pupil dilation. In at least some disclosed embodiments, the method further enables the image content to be differentiated distances from the viewer(s) and/or appears at several distances, optionally also simultaneously - e.g. B. with a hologram. Furthermore, the method enables the image content to be displayed downstream of the display device and upstream of the display device, possibly simultaneously, e.g. B. using a hologram.

What is important is that the light of the hologram itself (i.e. the holographic light) is transmitted to the viewer(s) - not a holographic reconstruction (i.e. an image) formed from the hologram. It can be said that the spatially modulated light received by the viewing system(s) is in the hologram domain and not in the spatial or image domain. It can also be said that the viewing system(s) performs the conversion of the hologram into an image. More specifically, an optical element such as e.g. B. the lens of each viewing system, the transformation through. In some embodiments, no holographic reconstruction or image is created between the display device and the viewing system(s). In some embodiments, a different hologram is computed and passed to each eye of a viewer, optionally using an interleaving scheme.

The display device has an active or display area with a first dimension which may be less than 10 cm, for example less than 5 cm or less than 2 cm. The propagation distance between the display device and the viewing system can be greater than 1 m, e.g. greater than 1.5m or greater than 2m. The optical propagation distance within the waveguide can be up to 2m, e.g. up to 1.5 m or up to 1 m. The method may be able to receive an image and determine a corresponding hologram of sufficient quality in less than 20 ms, e.g. B. in less than 15 ms or less than 10 ms.

The methods disclosed herein form a hologram configured to direct light into a plurality of channels, each channel corresponding to a different portion (i.e., sub-area) of an image. The hologram can be displayed on a display device, e.g. a spatial light modulator, i. H. are displayed. When displayed on a suitable display device, the hologram can spatially modulate light that is converted into an image by a viewing system. The channels formed by the diffractive structure are referred to here as "hologram channels" to make it clear that they are light channels that are encoded by the hologram with image information. It can be said that each channel's light is in the hologram domain and not in the image or space domain. In some embodiments, the hologram is a Fourier or Fourier transform hologram and the hologram domain is therefore the Fourier or frequency domain. The hologram can also be a Fresnel hologram or a Fresnel transform hologram.

The hologram is described here as directing the light into a plurality of hologram channels, just to make it clear that the image that can be reconstructed from the hologram is of finite size and can be arbitrarily divided into a plurality of sub-image regions, each hologram channel corresponding to a Image sub-area corresponds. Importantly, the hologram of this disclosure is characterized by how it distributes image content when illuminated. In particular, the hologram divides the image content according to the angle. That is, each point on the image is associated with a unique light ray angle or range of angles in the spatially modulated light formed by the hologram when illuminated - at least a unique pair of angles or range of angles, since the hologram is two-dimensional - that is, each point of a target/desired image can be associated with a channel of light formed by the hologram reconstructing the image. More specifically, the image content or information associated with each pixel is encoded in a respective channel. Provided there is no overlap, as described above, each pixel (or a contiguous area of pixels that forms a sub-area of the image) is uniquely assigned to a corresponding light channel. Each part of an image can therefore be associated with an angle (or a pair of angles) defining an axis of a discrete light channel formed by the hologram. For the avoidance of doubt, this behavior of the hologram is not conventional. The spatially modulated light formed by this particular type of hologram, when illuminated, can be randomly split into a plurality of hologram channels. From the foregoing, it can be seen that each hologram that can be viewed in spatially modulated light is associated with a corresponding portion or portion of the image. That is, all the information needed to reconstruct that portion or portion of the image is contained in a channel of spatially modulated light formed from the hologram of the image. When the spatially modulated light is viewed as a whole, there is not necessarily evidence of a multitude of discrete ones light channels. However, in some embodiments, a plurality of spatially separated hologram channels are formed by intentionally leaving areas of the target image from which the hologram is computed blank (ie, no image content is present).

Despite this, the hologram can still be identified. If e.g. B. only one hologram channel - i. H. only a coherent part or sub-area of the spatially modulated light formed by the hologram - reconstructed, only a corresponding sub-area of the image should be visible. If a different hologram channel - i.e. a different continuous part or sub-area of the spatially modulated light - is reconstructed, a different sub-area of the image should be visible in each case. Another distinguishing feature of this type of hologram is that the shape of the cross-sectional area of each hologram channel essentially corresponds to the shape of the entrance pupil (e.g. is essentially the same), although the size can be different - at least in the correct plane for which the hologram was calculated. Each light hologram channel propagates from the hologram in a core (or axial) direction. While these are just examples of how to characterize or identify this type of hologram, other methods can also be used. In summary, the hologram disclosed herein is characterized and identifiable by how the image content is distributed within the light encoded by the hologram, and the appended claims are formulated accordingly.

The method can consist of dividing the image during the hologram calculation in such a way that the number of light channels formed by the hologram - and thus the distance between the light channels - is synergistic with the replication process described here. In some embodiments, each channel uniquely corresponds to a number of reflection jumps within a waveguide. For example, a first channel may correspond to zero "bounces", a second channel to one "bounce", and so on.

The method described here offers many technical advances. First, the method does not generate ghosting, as can occur with other methods. This is because the method ensures from the outset that the correct image content goes to the right place by fully accounting for all possible light propagation paths in the waveguide. Second, the method, at least in some embodiments, can represent the image content at any arbitrary depth level, in contrast to other methods, which can be insufficient when the pixel spacing is very small. This is a significant problem in optical systems that use an optical combiner with optical power - such as e.g. B. a windshield of a vehicle - use to generate a virtual image. Third, the process inherently accounts for the effects of wavelength, so a color projector with multiple monochromatic holographic channels does not require image size correction by wavelength, as in the U.S. Patent 10,514,658 is described.

The various propagation paths of the hologram channels can each pass through the entrance aperture of the viewing system at different angles. The pupil expander can be arranged so that all hologram channels at each viewing position on a viewing plane pass through the entrance aperture of the viewing system. The pupil expander directs each hologram channel to the viewing system via only one propagation path for each valid viewing position. At least two of the plurality of hologram channels can partially overlap at the entrance aperture of the viewing system.

In embodiments where the disclosed method includes first through fifth stages, the first through fourth stages may be ordered stages. In the disclosed method, there is back-and-forth projection between the image plane and the hologram, and the method can start in the image plane or the hologram plane. The amplitude component of the light field is modified or restricted after each propagation into the image plane or the hologram plane, but the phase component is preserved. In some embodiments, the method begins with the first stage, which corresponds to beginning at the hologram plane. However, in other embodiments, the method begins with the third stage, which is equivalent to starting at the image plane. In these other embodiments, the third stage is followed by the fourth stage. The fourth stage is followed by the first stage and the first stage is followed by the second stage. Each stage can be performed once prior to hologram extraction, or at least some stages can be performed multiple times prior to hologram extraction.

The at least one light propagation path can consist of multiple light propagation paths provided by the pupillary dilation. The structure of the dilated pupil facilitates or allows for a variety of different possible light paths through it. The various possible light paths can partially overlap. In some embodiments, a series of ver different light paths, each light path in the series being longer than the last. Each light path of the series exits the pupil dilator at a different point on an exit surface thereof to create a corresponding series of light exit points or portions. The series of light exit points or sub-areas can be substantially uniformly arranged along the exit surface of the pupil dilator.

The pupil expander can be a waveguide pupil expander. Each ray of light entering the pupil expander can be repeated several times. The pupil expander can be arranged to propagate light by a series of internal reflections and emit light at a plurality of points along one of its major surfaces. Each light propagation path can be defined by the number of internal reflections within the waveguide associated with that light propagation path. For example, a first light propagation path may have no internal reflections and therefore corresponds to light passing directly through the waveguide. For example, a second light propagation path may include two internal reflections prior to exiting the waveguide, namely a first reflection at a first primary/reflective surface of the waveguide and a second reflection at a second primary/reflective surface of the waveguide, the second primary/reflective surface opposite or complementary to the first primary/reflective surface. Therefore, for the avoidance of doubt, the light propagation paths partially overlap. In other examples, a first light propagation path includes one reflection and the second light propagation path includes three reflections. The first light propagation path can be the shortest light propagation path and the nth light propagation path can be the longest light propagation path. The different propagation paths may traverse the entrance aperture of the viewing system at a different angle.

The at least one light propagation path can be only one of several light propagation paths provided by the pupil dilation. The first to fourth stages can be performed for each light propagation path of the plurality of light propagation paths to extract a hologram for each light propagation path. The first to fourth stages can be performed independently for each light propagation path. The multiple holograms corresponding to the multiple light propagation paths can be combined to form the hologram for display on the display device.

In particular, the method accounts for the plurality of light propagation paths through the waveguide by performing the first through fourth steps (regardless of starting point) for each light propagation path. The first to fourth steps can be carried out for each propagation path in sequence. Alternatively, the first step can be performed for each propagation path, then the second step for each propagation path, then the third step, and so on. Due to the partial overlap of the different propagation paths, the steps performed with respect to the nth propagation path can reuse calculations with respect to the n-1 propagation path, where the nth propagation path is the next longest propagation path after the n-1 propagation path. The multiple holograms determined for each of the multiple different light propagation paths can be combined by addition - particularly when the holograms are phase or phase-only holograms.

The light propagating from the display plane in the first stage may comprise a zeroth complex light field with a random phase component, a quadratic function, or a sampled quadratic function.

The amplitude component of the zeroth complex light field can be equal to that of the illumination beam. In some embodiments, the amplitude of the zeroth complex light field is equal to one. If the method starts with the first stage, the phase component of the zeroth complex light field can be random. The random phase distribution is also sometimes referred to as the random phase seed and can only be used as a starting point for the method when starting with the hologram plane (i.e. the first stage).

The first through fourth stages can be iteratively repeated before the step of extracting the hologram from the last iteration. The light emitted by the display device for the second and subsequent iterations may include the phase distribution of the fourth complex light field of the immediately preceding iteration.

If further iterations of the first stage are performed before the process is stopped (i.e. the hologram is acceptable), the phase component from the fourth stage will be retained or maintained or carried forward. That is, the phase component of the complex light field that has propagated into the display plane according to the first stage is equal to that of the fourth complex light field.

The hologram can be the phase component of the fourth data set. The hologram can be the phase component of the fourth data set of the last iteration or stage of the method. In some embodiments, the hologram is a kinoform or phase hologram or a pure phase hologram. The amplitude component of the fourth complex light field can be discarded.

The hologram may be a multi-image hologram. Each image can have a different image spacing. The second stage of the procedure can be performed independently for each image. It is important that the method described here generates a hologram that can generate image content on several levels at the same time. This is achieved by performing the second stage for each individual level and combining the results, e.g. B. by summing the complex light fields. Each image can be a real image or a virtual image. The image content can be visible in front of the display device—that is, downstream of the display device—and/or behind the display device—that is, upstream of the display device.

Each complex light field is determined by wave propagation optics such as Fresnel propagation, shifted Fresnel propagation, fractional Fresnel propagation, fractional Fourier transform or scaled Fast Fourier transform.

The modification of the amplitude component of the second stage can be to replace the amplitude component of the second complex light field with that of the image or to weight the amplitude component of the second complex light field based on the amplitude component of the image.

Each step of cropping may include cropping the complex field of light in accordance with at least one of the sizes and positions of the corresponding pupil. The size and/or position of the entrance pupil can be determined by tracking or monitoring the viewing system or by receiving information about the viewing system. In embodiments where the viewing system is an eye, the method may include eye tracking or head tracking. The first to fourth steps described here can be repeated if at least one property of the entrance pupil - such as position or size - changes.

The or each image may be a virtual image. The or each image may appear to be behind or beyond the display device to the viewing system. That is, the distance between the viewing system and the perceived image can be greater than the distance between the viewing system and the display device. In other embodiments, however, the image content is additionally or alternatively rendered downstream of the display device - i. H. between the display device and the viewing system(s) - shown.

The viewing system can be an eye of a viewer. The method may further include tracking the viewer's eye or head to determine at least the size and position of the entrance pupil of the viewing system. In some disclosed embodiments, the size and/or position of the entrance pupil(s) of the viewing system(s) is used as part of the method of determining the hologram. In some embodiments, the disclosed method is performed in real-time - e.g. B. with video rate - and the hologram is redefined, z. B. recalculated when the viewer moves or z. B. the ambient light conditions change, which affects the size of the viewer's entrance pupil.

The propagation along each light path provided by the pupil expander can include the combination of the individual complex light fields of the respective individual light paths. The individual complex light fields can be combined by addition. Each light propagation path of a variety of different light propagation paths provided by the pupil expander will be considered individually. The complex light field formed by each light path is determined individually.

The pupil expander can be a waveguide pupil expander. Each light propagation path corresponds to a different number of internal reflections within the waveguide. In some embodiments, the pupil expander is a waveguide pupil expander having a substantially one-dimensional (i.e., oblong) or two-dimensional shape (e.g., substantially planar, such as slab-shaped). In certain embodiments, the exit pupil is dilated in a longitudinal direction or dimension of the component. The pupil expander may have a pair of opposing or complementary reflective surfaces. One of these surfaces may be only partially reflective to allow light to escape at a series of light exit points or sub-areas.

The combination of the individual complex light fields can determine a lateral Include the position of each individual complex light field on a plane containing the entrance pupil. The number of internal reflections within the waveguide determines the lateral position.

Combining the individual complex light fields may further include determining an overall phase shift associated with the internal reflections of each light propagation path. This may involve the summation of a plurality of phase shifts associated with each light propagation path, each phase shift resulting from a reflection within the pupil dilator.

Also disclosed herein is a hologram engine configured to determine a hologram of an image for viewing by a head-up display. The head-up display includes a display device and a pupil dilator. The head-up display is configured to work with at least one viewing system. Each viewing system includes an entrance pupil in an entrance pupil plane, a lens in a lens plane, and a sensor in a sensor plane. The head-up display can be configured to interface with a pair of vision systems, such as B. a pair of eyes works. The display device (e.g. a spatial light modulator) is arranged to display the hologram. The pupil dilator is arranged to receive light that is spatially modulated in accordance with the hologram. For example, the displayed hologram may be illuminated with at least partially coherent light from a source. The display device spatially modulates the received light according to the displayed hologram. The hologram engine is arranged to determine a first complex field of light at the entrance pupil of a viewing system. The first complex field of light results from the propagation of light from a display plane of the display device along each light propagation path of the pupil dilator. The first complex light field also results from clipping in accordance with the entrance pupil of the viewing system. The hologram engine is further configured to determine a second complex light field in a sensor plane of a sensor of the viewing system. The second complex light field results from propagating the light of the first complex light field from the entrance pupil through a lens of the viewing system. The second complex light field also results from the modification of the amplitude component in accordance with the image. The hologram engine is further arranged to determine a third complex field of light at the entrance pupil. The third complex light field results from the propagation of the light of the second complex light field from the sensor plane back through the lens. The third complex light field also results from clipping in accordance with the entrance pupil. The hologram engine is further arranged to determine a fourth complex field of light in the display plane. The fourth complex light field results from propagating the light of the third complex light field back along each pupil dilator light propagation. The fourth complex light field also results from clipping in accordance with the display device. The hologram engine is set up to extract the hologram from the fourth data set. The hologram engine can reside in a display driver such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC). The display driver may be part of a picture generating unit ("PGU") for a head-up display ("HUD").

Aspects of the present disclosure relate to a hologram or kinoform characterized by the channeling or directing of holographic light. In particular, there is disclosed herein a diffractive structure arranged to spatially modulate light that can be converted into an image by a viewing system, the diffractive structure being configured to direct light into a plurality of hologram channels, each hologram channel corresponds to a different part of the image.

The diffractive structure can be displayed on a display device such as a spatial light modulator, e.g. B. a spatial light modulator (SLM) with liquid crystals on silicon (LCOS). When the display device displaying the diffractive structure is suitably illuminated, the diffractive structure is configured to spatially modulate the light such that the light emitted by the display device is directed into the plurality of hologram channels. A single (i.e. common) light source can be used to illuminate the entire diffractive structure. The diffractive structure may include a plurality of pixels, with each pixel of the diffractive structure contributing light to each of the hologram channels.

Instead, the hologram channels can also be referred to as "holographic channels" because they consist of light channels that have been spatially modulated by the diffractive structure.

The diffractive structure can be arranged such that the hologram channels propagate at different angles from the diffractive structure. That is, each hologram channel is through one unique axis angle or pair of angles with respect to the display device described above. Each of these angles can be between a primary or central direction of movement of the respective channel and a point on the display device, e.g. B. a central point on the display device on which the diffractive structure is displayed. Each pixel of the hologram or diffractive structure can contribute to each channel.

Each hologram channel can basically contain spatially modulated light corresponding to a different part of the image. The word "mainly" is used to indicate that there may be some overlap between channels, but it is relatively small. For example, a first channel may generally (i.e., generally or substantially) correspond to a first angular portion of the field of view (i.e., image), and a second channel may generally or substantially correspond to a second angular portion of the field of view (i.e., image), but it there may be a partial overlap between the first and second angle sections. That is, the first channel and the second channel can both encode information of an overlapping area of the field of view.

Each channel corresponds to a sub-area of the image (i.e. an angular range of the field of view). While there may be a partial overlap between the sub-regions (as described above), each channel is uniquely associated with a point in the field of view that is the center of the corresponding sub-region. In some embodiments, the sub-regions are the same size and/or shape. In other embodiments, the portions have different sizes and/or shapes. In some embodiments, the shape of each sub-area is determined by the shape of the display device, more specifically by the shape of the area bounding the pixel array.

The diffractive structure can be designed to spatially modulate the phase of the light.

The diffractive structure can be designed to direct the light through a waveguide. The waveguide can be set up for pupil dilation or pupil multiplication.

The cross-sectional shape of the light pattern that can be formed by each hologram channel can correspond substantially to the shape of an entrance aperture of the viewing system. The size of the cross-section of each channel can also correspond substantially to the size of the entrance opening when the cross-section is viewed in the plane of the entrance opening. The cross-section may be dimensioned to be similar in size to, but larger than, the entrance opening when the cross-section is viewed in the plane of the entrance opening.

The hologram channels can be spatially separated or at least partially spatially separated. The channels may fan out or diverge to separate spatially as they propagate from the diffractive structure toward a viewer or viewing system. In some embodiments, the channels fan out in only one direction/dimension, e.g. B. in the horizontal direction.

Also disclosed herein is a system that includes the diffractive structure, a waveguide arranged to receive the spatially modulated light from the diffractive structure, and a viewing system arranged to receive the spatially modulated light across the waveguide receives.

The system can be set up so that the light of each hologram channel takes a different optical path from the diffractive structure to the viewing system.

The different optical paths may involve a different number of reflections within the waveguide. The different optical paths can have different lengths. The various optical paths may pass through the entrance aperture of the viewing system at different angles.

The waveguide can be arranged so that all hologram channels at each viewing position on a viewing plane pass through the input aperture of the viewing system. The waveguide must only guide each hologram channel through one optical path to the viewing system for each permissible viewing position.

At least two of the plurality of hologram channels can partially overlap at the entrance aperture of the viewing system.

The diffractive structure can be a kinoform or a hologram. It can be a computer generated hologram. A hologram engine or other controller or processor may be provided to output signals to drive a display device to display the diffractive structure.

The term "hologram" refers to the recording that contains amplitude or phase information, or a combination thereof, about the object. The term "holographic reconstruction" refers to the optical reconstruction of the object created by illuminating the hologram. The system described here is called a "holographic projector" because the holographic reconstruction can be a real image and is spatially separated from the hologram. The term "display field" refers to the 2D area in which the holographic reconstruction is formed and fully focused. When the hologram is displayed on a pixelated spatial light modulator, the display panel is repeated as a plurality of diffracted orders, each diffracted order being a zero-order replica of the display panel. The zero-order display panel generally corresponds to the preferred or primary display panel because it is the brightest display panel. Unless expressly stated otherwise, the term "replayfield" refers to the zero-order replayfield. The term "playback plane" refers to the plane in space that contains all the playfields. The terms "image", "replay image" and "image area" refer to areas of the display field that are illuminated by the light of the holographic reconstruction. In some embodiments, the "image" may consist of individual points, which may be referred to as "image points" or, for the sake of simplicity, "image pixels".

The terms "encoding", "writing" or "addressing" are used to describe the process of providing the plurality of pixels of the SLM with a corresponding plurality of control values, each of which determines the degree of modulation of each pixel. The pixels of the SLM can be said to be configured to "display" a light modulation distribution in response to receiving the multiple control values. Thus, the SLM can be said to "display" a hologram, and the hologram can be viewed as an array of light modulation values or levels.

It has been shown that a holographic reconstruction of acceptable quality can be made from a "hologram" that contains only phase information related to the original object (i.e. the target image for the reconstruction). Such a holographic recording can be referred to as a pure phase hologram. The embodiments relate to a pure phase hologram, but the present disclosure is also applicable to pure amplitude holography. The present disclosure is not limited to any particular method of hologram calculation. Some embodiments relate to point cloud holograms - i. H. Holograms created with point cloud methods - just as an example. However, the present disclosure is equally applicable to Fourier or Fresnel holograms and to holograms computed by other methods such as coherent ray tracing.

The present disclosure also applies to forming a holographic reconstruction using amplitude and phase information related to the original object (i.e., the target image). In some embodiments, this is achieved through complex modulation using a so-called full complex hologram that contains both amplitude and phase information related to the original object. Such a hologram can be called a full complex hologram because the value (gray level) assigned to each pixel of the hologram has an amplitude and a phase component. The value (gray level) assigned to each pixel can be represented as a complex number that has both amplitude and phase components. In some embodiments, a fully complex computer generated hologram is computed.

It can be referred to as the phase value, phase component, phase information, or simply the phase of the pixels of the computer generated hologram or spatial light modulator as short for "phase delay". That is, each phase value described is actually a number (e.g., ranging from 0 to 2⍰) that represents the amount of phase delay provided by that pixel. For example, a spatial light modulator pixel with a phase value of π/2 retards the phase of the received light by π/2 radians. In some embodiments, each pixel of the spatial light modulator can be operated with one of several possible modulation values (e.g. phase delay values). The term "grayscale" can be used to refer to the variety of levels of modulation available. For example, the term "gray level" can be used for convenience to refer to the variety of phase levels available in a pure phase modulator, even though different phase levels do not result in different shades of gray. The term "grayscale" can also be used for convenience to refer to the variety of complex modulation levels available in a complex modulator.

The hologram therefore consists of a series of gray levels, ie a series of light modulation values, e.g. B. a series of phase delay values or complex modulation values. The hologram is also considered a diffractive pattern because it is a pattern that causes diffraction when displayed on a spatial light modulator and illuminated with light whose wavelength is comparable to, but generally smaller than, the pixel pitch of the spatial light modulator. Reference is made here to the combination of the hologram with other diffraction patterns, e.g. B. with diffraction patterns that function as a lens or grating. For example, a diffractive pattern acting as a grating can be combined with a hologram to shift the display field on the display plane, or a diffractive pattern acting as a lens can be combined with a hologram to optimize the holographic reconstruction to a to focus the reproduction plane in the near field.

Although various embodiments and groups of embodiments may be disclosed separately in the following detailed description, any feature of an embodiment or group of embodiments may be combined with any other feature or combination of features of an embodiment or group of embodiments. That is, all possible combinations and permutations of features disclosed in the present disclosure are contemplated.

1. 1. Eine Lichtmaschine, die so angeordnet ist, dass sie ein Betrachtungssystem mit einer Eintrittspupille mit räumlich moduliertem Licht versorgt, wobei das Anzeigesystem umfasst:
   • eine Anzeigevorrichtung, die so beschaffen ist, dass sie ein Hologramm anzeigt und Licht in Übereinstimmung mit dem Hologramm räumlich moduliert; und
   • eine Hologramm-Maschine, die so angeordnet ist, dass sie Beitragsinformationen empfängt, die beitragende und nicht beitragende Bereiche der Anzeigevorrichtung auf der Grundlage des Ortes der Eintrittspupille identifizieren, wobei die beitragenden Bereiche der Anzeigevorrichtung im Wesentlichen räumlich moduliertes Licht ausbreiten, das durch die Eintrittspupille an dem Ort hindurchgeht, und nicht beitragende Bereiche der Anzeigevorrichtung im Wesentlichen räumlich moduliertes Licht ausbreiten, das von der Eintrittspupille an dem Ort aufgehalten wird,
   • wobei die Beitragsinformation ferner (i) mindestens einen primär beitragenden Bereich der Anzeigevorrichtung, der Licht zum Betrachtungssystem ausbreitet, der zu einem Primärbild beiträgt, und (ii) mindestens einen sekundär beitragenden Bereich der Anzeigevorrichtung, der Licht zum Betrachtungssystem ausbreitet, der zu einem Sekundärbild beiträgt, identifiziert, wobei
   • die Hologramm-Maschine ist ferner so eingerichtet, dass sie ein Hologramm auf der Grundlage des mindestens einen primären beitragenden Bereichs der Anzeigevorrichtung bestimmt und das Hologramm zur Anzeige an die Anzeigevorrichtung ausgibt.
2. 2. Lichtmaschine gemäß Punkt 1, wobei die Lichtmaschine ferner ein Überwachungssystem umfasst, das so angeordnet ist, dass es den Ort der Eintrittspupille des Betrachtungssystems bestimmt.
3. 3. Lichtmaschine gemäß Punkt 1 oder Punkt 2, wobei die Lichtmaschine ferner einen Wellenleiter umfasst, der so angeordnet ist, dass er das räumlich modulierte Licht von der Anzeigevorrichtung empfängt und eine Vielzahl unterschiedlicher Lichtausbreitungspfade für das räumlich modulierte Licht von der Anzeigevorrichtung zur Eintrittspupille bereitstellt, wobei jeder beitragende Bereich einem unterschiedlichen jeweiligen Lichtausbreitungspfad entspricht, der von dem Wellenleiter bereitgestellt wird.
4. 4. Lichtmaschine nach einem der Punkte 1 bis 3, wobei das Betrachtungssystem so angeordnet ist, dass es ein dem Hologramm entsprechendes Bild erzeugt.
5. 5. Eine Lichtmaschine wie in Punkt 4, wobei das Primärbild eine erste Version des Bildes und das Sekundärbild eine zweite Version des Bildes umfasst.
6. 6. Lichtmaschine wie in einem der vorangehenden Punkte, wobei die Beitragsinformation jeweilige beitragende und nicht beitragende Bereiche der Anzeigevorrichtung für jeden einer Vielzahl von Bildpunkten des Bildes identifiziert.
7. 7. Eine Lichtmaschine wie in Punkt 6, wobei das Hologramm eine Vielzahl von Teilhologrammen umfasst, wobei jedes Teilhologramm von der Hologrammmaschine auf der Grundlage der Beitragsinformation eines jeweiligen Bildpunktes des Bildes bestimmt wird.
8. 8. Verfahren zum Bestimmen eines Hologramms zur Anzeige auf einer Anzeigevorrichtung, wobei das Verfahren umfasst:
   1. (i) Bestimmung des Ortes der Eintrittspupille eines Betrachtungssystems, das für die Betrachtung des Hologramms eingerichtet ist;
   2. (ii) Identifizieren von beitragenden Bereichen und nicht beitragenden Bereichen der Anzeigevorrichtung, wobei die beitragenden Bereiche der Anzeigevorrichtung im Wesentlichen Licht ausbreiten, das durch die Eintrittspupille des Betrachtungssystems an dem bestimmten Ort hindurchgeht, und nicht beitragende Bereiche der Anzeigevorrichtung im Wesentlichen Licht ausbreiten, das durch die Eintrittspupille des Betrachtungssystems an dem bestimmten Ort aufgehalten wird; und
   3. (iii) Identifizieren mindestens eines primären beitragenden Bereichs der Anzeigevorrichtung, der Licht liefert, das zu einem Primärbild beiträgt, und mindestens eines sekundären beitragenden Bereichs der Anzeigevorrichtung, der Licht liefert, das zu einem Sekundärbild beiträgt; und
   4. (iv) Bestimmen des Hologramms auf der Grundlage des mindestens einen primär beitragenden Bereichs der Anzeigevorrichtung.
9. 9. Verfahren zum Bestimmen eines Hologramms wie in Punkt 8, wobei die Schritte (ii) bis (iv) für jeden Bildpunkt einer Vielzahl von Bildpunkten des Bildes ausgeführt werden und wobei das Bestimmen eines Ortes jedes beitragenden Bereichs für jeden Bildpunkt das Identifizieren eines Ortes umfasst, an dem ein Lichtstrahl, der sich von dem Bildpunkt zu der Eintrittspupille bewegt, die Anzeigevorrichtung schneidet.
10. 10. Verfahren zum Bestimmen eines Hologramms gemäß Punkt 8 oder 9, wobei das Betrachtungssystem einen Wellenleiter umfasst, der so angeordnet ist, dass er räumlich moduliertes Licht von der Anzeigevorrichtung empfängt und eine Vielzahl verschiedener Lichtausbreitungspfade für das räumlich modulierte Licht von der Anzeigevorrichtung zur Eintrittspupille bereitstellt, und wobei der Schritt (iii) für jeden Bildpunkt das Bestimmen einer Anzahl interner Reflexionen, B, innerhalb der Wellenleiter-Pupillenerweiterung entsprechend dem Primärbild umfasst.
11. 11. Verfahren gemäß Punkt 10, wobei der Schritt des Bestimmens der Anzahl der internen Reflexionen (B) auf einem Winkel basiert, der dem entsprechenden Bildpunkt zugeordnet ist, wobei der Winkel der Winkel zur optischen Achse einer Linie ist, die durch Extrapolieren einer Linie, die den Mittelpunkt der Anzeigevorrichtung und die bestimmte Eintrittspupillenposition verbindet, auf das Bild gebildet wird.
12. 12. Verfahren gemäß Punkt 11, bei dem jeder beitragende Bereich eine Größe hat, die auf dem Durchmesser der Eintrittspupille basiert.
13. 13. Verfahren wie in einem der Punkte 8 bis 12, wobei die Schritte (ii) und (iii) für jeden Bildpunkt umfassen:
    • Strahlenverfolgung vom Bildpunkt [_xvirtuell, _yvirtuell, _zvirtuell] zu einer Betrachtungsebene des Betrachtungssystems für B-Lichtreflexionen innerhalb des Wellenleiters, um eine Position [_xsensor, _ysensor] auf der Betrachtungsebene zu identifizieren;
    • Bestimmung der Koordinaten [x_LCOS (B), y_LCOS (B)] des Hauptlichtstrahls an der Anzeigevorrichtung für die Lichtausbreitung mit B-Reflexionen vom Bildpunkt [_xvirtuell, _yvirtuell, _zvirtuell] zur Position [_xsensor, _ysensor] in der Betrachtungsebene; und
    • Identifizierung aktiver Pixel der Anzeigevorrichtung innerhalb eines durch [x_LCOS (B), y_LCOS (B)] definierten Bereichs.
14. 14. Verfahren nach einem der Punkte 8 bis 13, wobei der Schritt (iv) die Bestimmung eines oder mehrerer Werte für das Hologramm nur in dem mindestens einen primär beitragenden Bereich der Anzeigevorrichtung umfasst.
15. 15. Verfahren nach einem der Punkte 8 bis 13, das ferner den Ausschluss von Werten für das Hologramm in einem Bereich der Anzeigevorrichtung umfasst, der nicht in dem primären beitragenden Bereich enthalten ist.
16. 16. Verfahren zur Bestimmung eines Hologramms nach einem der Punkte 8 bis 13, wobei Schritt (iv) das Ausschließen von Hologrammwerten, die mit mindestens einem sekundären beitragenden Bereich verbunden sind, während der Bestimmung des Hologramms umfasst.
17. 17. Verfahren zur Bestimmung eines Hologramms nach einem der Punkte 8 bis 13, wobei der Schritt (iv) die Beschränkung der Hologrammbestimmung ausschließlich auf den mindestens einen primär beitragenden Bereich der Anzeigevorrichtung umfasst.
18. 18. Verfahren zum Bestimmen eines Hologramms wie in einem der Punkte 8 bis 17, wobei Schritt (iv) das Bestimmen eines Teilhologramms innerhalb des jeweiligen mindestens einen primären beitragenden Bereichs für jeden Bildpunkt und das Kombinieren der Teilhologramme zum Bilden des Hologramms umfasst.
19. 19. Verfahren zur Bestimmung eines Hologramms gemäß Punkt 18, wobei jedes Teilhologramm eine Amplituden- und/oder Phasenhologrammkomponente umfasst, die durch Ausbreitung einer Lichtwelle von [_xvirtuell, _yvirtuell, _zvirtuell] zu dem entsprechenden primären Beitragsbereich bestimmt wird.
20. 20. Verfahren zur Bestimmung eines Hologramms nach einem der Punkte 8 bis 13, bei dem für jeden Bildpunkt ein zusätzlicher Bereich der Anzeigevorrichtung identifiziert wird, der zu B+DB-Aufprallvorgängen beiträgt.
21. 21. Verfahren zum Bestimmen eines Hologramms wie in Punkt 20, wobei das Identifizieren eines zusätzlichen beitragenden Bereichs umfasst:
    • Strahlenverfolgung zurück von [_xsensor, _ysensor] zur virtuellen Bildebene_zvirtual für B+ΔB Bounces;
      • Bestimmung der virtuellen Punktkoordinaten [_xvirtuell(DB),_yvirtuell(DB), _zvirtuell], die für B+DB-Reflexionen auf [_xsensor, _ysensor] abgebildet werden;
      • Bestimmung der Koordinaten [x_LCOS (B+ΔB), y_LCOS (B+ΔB)] eines Hauptstrahls an der Anzeigevorrichtung für die Lichtausbreitung von [_xvirtuell(DB), _yvirtuell(DB), _zvirtuell] zur Betrachtungsebene mit B+DB-Bounces; und
      • Identifizierung zusätzlicher aktiver Pixel der Anzeigevorrichtung innerhalb eines zweiten Bereichs, der durch [x_LCOS (B+ΔB), y_LCOS (B+ΔB)] definiert ist.
22. 22. Verfahren zur Bestimmung eines Hologramms gemäß Punkt 21, das ferner die Bestimmung eines zusätzlichen Teilhologramms für jedes zusätzliche aktive Pixel und die Kombination der zusätzlichen Teilhologramme mit den Teilhologrammen umfasst.
23. 23. Verfahren zur Bestimmung eines Hologramms wie in Punkt 22, wobei jedes zusätzliche Teilhologramm eine Amplituden- und/oder Phasenhologrammkomponente umfasst, die durch Ausbreitung einer Lichtwelle von [_xvirtuell(DB), _yvirtuell(DB), _zvirtuell] zu dem zusätzlichen beitragenden Bereich bestimmt wird.
24. 24. Eine Lichtmaschine oder ein Verfahren zur Bestimmung eines Hologramms wie in einem der vorhergehenden Punkte, wobei das Hologramm so konfiguriert ist, dass das primäre Bild und mindestens ein sekundäres Bild virtuelle Bilder sind, die jeweils einen nicht-unendlichen virtuellen Bildabstand haben.
25. 25. Lichtmaschine oder Verfahren zum Bestimmen eines Hologramms wie im vorhergehenden Punkt, wobei eine Anzeigefläche der Anzeigevorrichtung eine erste Abmessung von weniger als 5 cm, wie weniger als 2 cm oder weniger als 1 cm, aufweist.
26. 26. Eine Lichtmaschine oder ein Verfahren zur Bestimmung eines Hologramms wie im vorhergehenden Punkt, wobei ein Abstand von der Anzeigevorrichtung zur Eintrittspupille des Betrachtungssystems gleich oder größer als 20 cm oder 50 cm, wie z.B. größer als 75 cm oder größer als 100 cm ist.
27. 27. Lichtmaschine oder Verfahren zum Bestimmen eines Hologramms wie in einem der vorhergehenden Punkte, wobei ein Wellenleiter so angeordnet ist, dass er räumlich moduliertes Licht von der Anzeigevorrichtung empfängt, und wobei das primäre Bild ein ausgewähltes Bild aus einer Vielzahl von durch den Wellenleiter gebildeten Bildern ist, das die größte Leuchtdichte aufweist.

The following numbered items are also revealed:

1. 1. An alternator arranged to provide spatially modulated light to a viewing system having an entrance pupil, the display system comprising:
   • a display device arranged to display a hologram and spatially modulate light in accordance with the hologram; and
   • a hologram engine arranged to receive contribution information identifying contributing and non-contributing areas of the display based on the location of the entrance pupil, the contributing areas of the display substantially propagating spatially modulated light passing through the entrance pupil passes through the location, and non-contributing areas of the display propagate substantially spatially modulated light stopped by the entrance pupil at the location,
   • wherein the contribution information further (i) at least one primary contributing area of the display device that spreads light to the viewing system that contributes to a primary image, and (ii) at least one secondary contributing area of the display device that spreads light to the viewing system that contributes to a secondary image , identified where
   • the hologram engine is further configured to determine a hologram based on the at least one primary contributing area of the display device and to output the hologram to the display device for display.
2. 2. The alternator according to item 1, wherein the alternator further comprises a monitoring system arranged to determine the location of the entrance pupil of the viewing system.
3. 3. The light engine according to item 1 or item 2, wherein the light engine further comprises a waveguide arranged to receive the spatially modulated light from the display device and to provide a plurality of different light propagation paths for the spatially modulated light from the display device to the entrance pupil, each contributing region corresponding to a different respective light propagation path provided by the waveguide.
4. 4. Alternator according to any one of items 1 to 3, wherein the viewing system is arranged to produce an image corresponding to the hologram.
5. 5. An alternator as in item 4, wherein the primary image comprises a first version of the image and the secondary image comprises a second version of the image.
6. 6. An alternator as in any preceding item, wherein the contribution information identifies respective contributing and non-contributing areas of the display device for each of a plurality of pixels of the image.
7. 7. A light engine as in item 6, wherein the hologram comprises a plurality of sub-holograms, each sub-hologram being determined by the hologram engine based on the contribution information of a respective pixel of the image.
8. 8. A method of designating a hologram for display on a display device, the method comprising:
   1. (i) determining the location of the entrance pupil of a viewing system arranged to view the hologram;
   2. (ii) Identifying contributing areas and non-contributing areas of the display, wherein the contributing areas of the display substantially spread light that passes through the entrance pupil of the viewing system at the particular location, and non-contributing areas of the display substantially spread light that passes through stopping the entrance pupil of the viewing system at the specified location; and
   3. (iii) identifying at least one primary contributing area of the display device that provides light that contributes to a primary image and at least one secondary contributing area of the display device that provides light that contributes to a secondary image; and
   4. (iv) determining the hologram based on the at least one primary contributing area of the display device.
9. 9. A method of determining a hologram as in item 8, wherein steps (ii) through (iv) are performed for each pixel of a plurality of pixels of the image and wherein determining a location of each contributing region for each pixel comprises identifying a location , where a ray of light traveling from the pixel to the entrance pupil intersects the display device.
10. 10. A method for determining a hologram according to item 8 or 9, wherein the viewing system comprises a waveguide arranged to receive spatially modulated light from the display device and to provide a plurality of different light propagation paths for the spatially modulated light from the display device to the entrance pupil , and wherein step (iii) comprises, for each pixel, determining a number of internal reflections, B, within the waveguide pupil dilation corresponding to the primary image.
11. 11. Method according to item 10, wherein the step of determining the number of internal reflections (B) is based on an angle associated with the corresponding pixel, the angle being the angle to the optical axis of a line obtained by extrapolating a line, connecting the center of the display device and the determined entrance pupil position onto which the image is formed.
12. 12. The method of item 11, wherein each contributing region has a size based on the diameter of the entrance pupil.
13. 13. Method as in any one of items 8 to 12, wherein steps (ii) and (iii) comprise for each pixel:
    • ray tracing from pixel [ _xvirtual , _yvirtual , _zvirtual ] to a viewing system viewing plane for B light reflections within the waveguide to identify a position [ _xsensor , _ysensor ] on the viewing plane;
    • determining the coordinates [x _LCOS (B), y _LCOS (B)] of the main light beam at the display device for light propagation with B reflections from the pixel [ _xvirtual , _yvirtual , _zvirtual ] to the position [ _xsensor , _ysensor ] in the viewing plane; and
    • Identification of active pixels of the display device within an area defined by [x _LCOS (B), y _LCOS (B)].
14. 14. The method according to any one of items 8 to 13, wherein step (iv) comprises determining one or more values for the hologram only in the at least one primary contributing area of the display device.
15. 15. The method of any one of items 8 to 13, further comprising excluding values for the hologram in an area of the display device that is not included in the primary contributing area.
16. 16. A method of determining a hologram according to any one of items 8 to 13, wherein step (iv) comprises excluding hologram values associated with at least one secondary contributing region during the determination of the hologram.
17. 17. The method for determining a hologram according to any one of points 8 to 13, wherein step (iv) comprises restricting the hologram determination exclusively to the at least one primarily contributing area of the display device.
18. 18. A method of determining a hologram as in any one of items 8 to 17, wherein step (iv) comprises determining a partial hologram within the respective at least one primary contributing region for each pixel and combining the partial holograms to form the hologram.
19. 19. A method for determining a hologram according to item 18, wherein each sub-hologram comprises an amplitude and/or phase hologram component determined by propagating a lightwave from [ _xvirtual , _yvirtual , _zvirtual ] to the corresponding primary contribution region.
20. 20. Method of determining a hologram according to any one of items 8 to 13, in which an additional area of the display device that contributes to B+DB impact events is identified for each pixel.
21. 21. A method of determining a hologram as in item 20, wherein identifying an additional contributing region comprises:
    • Ray tracing back from [ _xsensor , _ysensor ] to virtual image plane _zvirtual for B+ΔB bounces;
      • Determination of the virtual point coordinates [ _xvirtual (DB), _yvirtual (DB), _zvirtual ], which are mapped to [ _xsensor , _ysensor ] for B+DB reflections;
      • Determine the coordinates [x _LCOS (B+ΔB), y _LCOS (B+ΔB)] of a principal ray at the display device for light propagation from [ _xvirtual (DB), _yvirtual (DB), _zvirtual ] to the viewing plane with B+DB bounces ; and
      • Identify additional active pixels of the display device within a second region defined by [x _LCOS (B+ΔB), y _LCOS (B+ΔB)].
22. 22. A method of determining a hologram according to item 21, further comprising determining an additional sub-hologram for each additional active pixel and combining the additional sub-holograms with the sub-holograms.
23. 23. A method of determining a hologram as in item 22, wherein each additional sub-hologram comprises an amplitude and/or phase hologram component determined by propagating a lightwave from [ _xvirtual (DB), _yvirtual (DB), _zvirtual ] to the additional contributing region becomes.
24. 24. An alternator or method for determining a hologram as in any preceding item, wherein the hologram is configured such that the primary image and at least one secondary image are virtual images each having a non-infinite virtual image spacing.
25. 25. Light machine or method for determining a hologram as in the previous point, wherein a display surface of the display device has a first dimension of less than 5 cm, such as less than 2 cm or less than 1 cm.
26. 26. An alternator or method for determining a hologram as in the preceding item, wherein a distance from the display device to the entrance pupil of the viewing system is equal to or greater than 20 cm or 50 cm, such as greater than 75 cm or greater than 100 cm.
27. 27. An alternator or method of determining a hologram as in any preceding item, wherein a waveguide is arranged to receive spatially modulated light from the display device, and wherein the primary image is a selected one of a plurality of images formed by the waveguide is which has the greatest luminance.

character list

• 1 ist eine schematische Darstellung eines reflektierenden SLM, der eine holografische Rekonstruktion auf einem Bildschirm erzeugt;
• 2A zeigt eine erste Iteration eines Beispielalgorithmus vom Typ Gerchberg-Saxton;
• 2B zeigt die zweite und die folgenden Iterationen des Beispielalgorithmus vom Typ Gerchberg-Saxton;
• 2C zeigt alternative zweite und weitere Iterationen des Gerchberg-Saxton-Beispielalgorithmus;
• 3 ist eine schematische Darstellung eines reflektierenden LCOS-SLM;
• 4 zeigt den Winkelinhalt von Animationen, die sich über ein kleines Sichtfenster in Richtung einer Blende ausbreiten;
• 5a zeigt ein Betrachtungssystem mit einer relativ geringen Ausbreitungsdistanz;
• 5b zeigt ein Betrachtungssystem mit einer relativ großen Ausbreitungsdistanz;
• 6a zeigt ein Betrachtungssystem mit einer relativ großen Ausbreitungsdistanz, das einen Wellenleiter enthält, um ein virtuelles Bild im Unendlichen zu erzeugen;
• 6b zeigt eine vergrößerte Ansicht der optischen Pfade von 6a;
• 7 zeigt, wie mit einem endlichen virtuellen Bild und einem Wellenleiter-Pupillenexpander Geisterbilder erzeugt werden können;
• 8 zeigt ein virtuelles Bild, das aus einem Primärbild und zwei Geisterbildern besteht;
• Die 9A bis 9C zeigen ein Beispiel, bei dem das gesamte LCOS verwendet wird, um einen Primärbildpunkt und zwei entsprechende Geisterbildpunkte zu erzeugen;
• Die 10A bis 10C zeigen einen ersten, einen zweiten und einen dritten Ausbreitungspfad durch einen Wellenleiter, die jeweils zu einem zweiten Geisterpunkt, einem Hauptbildpunkt und einem ersten Geisterpunkt führen;
• Die 11A bis 11C zeigen den Ausbreitungsweg und die LCOS-Nutzung in Bezug auf drei verschiedene Feld-/Bildpunkte;
• 12A zeigt ein Betrachtungssystem mit einem virtuellen Bildpunkt und einem Bild dieses virtuellen Bildpunkts, das durch ein Betrachtungssystem und einen Wellenleiter gebildet wird;
• 12B zeigt den primär beitragenden Bereich des LCOS in Bezug auf das Beispiel von 12A;
• 13 zeigt ein Flussdiagramm eines verbesserten Verfahrens zur Ableitung einer verbesserten Datenstruktur gemäß den Ausführungsformen;
• 14 zeigt ein Flussdiagramm einer weiteren verbesserten Methode zur Ableitung einer verbesserten Datenstruktur in Übereinstimmung mit Ausführungsformen;
• 15 zeigt ein optisches System gemäß den Ausführungsformen;
• 16 ist ein Flussdiagramm, das die Schritte eines Verfahrens in Übereinstimmung mit den Ausführungsformen zeigt;
• 17A zeigt ein Bild mit einer Vielzahl von Bildbereichen (unten) und ein entsprechendes Hologramm mit einer Vielzahl von Hologrammkomponenten (oben);
• 17B zeigt ein Hologramm gemäß der vorliegenden Offenbarung, gekennzeichnet durch die Lenkung oder Kanalisierung von holografisch kodiertem Licht in eine Vielzahl von diskreten Hologrammkanälen; und
• 17C zeigt ein optimiertes System, bei dem der Lichtinhalt jedes Hologrammkanals über einen anderen optischen Pfad zum Auge geleitet wird.

Specific embodiments are described by way of example only with reference to the following figures:

• 1 Figure 12 is a schematic representation of a reflective SLM producing a holographic reconstruction on a screen;
• 2A Figure 12 shows a first iteration of an example Gerchberg-Saxton algorithm;
• 2 B Figure 12 shows the second and subsequent iterations of the example Gerchberg-Saxton algorithm;
• 2C shows alternative second and further iterations of the example Gerchberg-Saxton algorithm;
• 3 Figure 12 is a schematic representation of a reflective LCOS SLM;
• 4 shows the angular content of animations propagating across a small viewing window towards a gate;
• 5a shows a viewing system with a relatively short propagation distance;
• 5b shows a viewing system with a relatively large propagation distance;
• 6a Fig. 1 shows a viewing system with a relatively long propagation distance that includes a waveguide to create a virtual image at infinity;
• 6b shows an enlarged view of the optical paths of FIG 6a ;
• 7 shows how ghost images can be generated using a finite virtual image and a waveguide pupil expander;
• 8th shows a virtual image composed of a primary image and two ghost images;
• The 9A until 9C show an example where the entire LCOS is used to generate a primary pixel and two corresponding ghost pixels;
• The 10A until 10C show first, second and third propagation paths through a waveguide leading to a second ghost spot, a main pixel and a first ghost spot, respectively;
• The 11A until 11C show propagation path and LCOS usage in relation to three different field/pixel points;
• 12A shows a viewing system with a virtual pixel and an image of this virtual pixel formed by a viewing system and a waveguide;
• 12B shows the primary contributing area of the LCOS relative to the example of 12A ;
• 13 12 shows a flow diagram of an improved method for deriving an improved data structure according to embodiments;
• 14 12 shows a flow diagram of another improved method for deriving an improved data structure, in accordance with embodiments;
• 15 12 shows an optical system according to the embodiments;
• 16 Fig. 12 is a flow chart showing the steps of a method in accordance with the embodiments;
• 17A shows an image with a plurality of image areas (bottom) and a corresponding hologram with a plurality of hologram components (top);
• 17B Figure 12 shows a hologram in accordance with the present disclosure characterized by directing or channeling holographically encoded light into a plurality of discrete hologram channels; and
• 17C shows an optimized system in which the light content of each hologram channel is directed to the eye via a different optical path.

The same reference numbers are used throughout the drawings to refer to the same or like parts.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention is not limited to the embodiments described below, but extends to the full scope of the appended claims. That is, the present invention may be embodied in various forms and should not be construed as limited to the described embodiments, which are presented for purposes of illustration.

Unless otherwise specified, terms in the singular may also be used in the plural.

A structure described as lying on top/bottom of another structure or on top/under the other structure should be understood to include a case where the structures touch each other and also a case in which with a third structure interposed therebetween.

When describing a temporal relationship -- for example, when describing the temporal sequence of events as "after," "then," "next," "before," or the like -- it should be understood that this disclosure describes continuous events as opposed to continuous events includes unless otherwise noted. For example, the description should be assumed to include a non-continuous case unless phrases such as "straight," "immediate," or "direct" are used.

Although the terms "first," "second," etc. may be used herein to describe various elements, those elements are not limited by those terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and likewise a second element could be termed a first element, without departing from the scope of the appended claims.

Some or all of the features of various embodiments may be coupled or combined with one another and may interact with one another in various ways. Some embodiments may be executed independently or together in a co-dependent relationship.

Optical configuration

1 Figure 12 shows an embodiment in which a computer generated hologram is encoded with a single spatial light modulator. The computer generated hologram is a Fourier transform of the object to be reconstructed. It will be appreciated that this is just an example and other methods of computer generation are also within the scope of the present disclosure tion of the hologram should be considered. The hologram can therefore be said to be a representation of the object in the Fourier or frequency domain or in the spectral domain. In this embodiment, the spatial light modulator is a reflective liquid crystal-on-silicon, "LCOS" device. The hologram is encoded on the spatial light modulator and a holographic reconstruction is performed on a display panel, e.g. B. a light receiving surface such as a screen or a diffuser generated.

A light source 110 , for example a laser or a laser diode, is arranged to illuminate the SLM 140 via a collimating lens 111 . The collimating lens causes a generally planar wavefront of light to impinge on the SLM. In 1 the direction of the wavefront is not normal (e.g. two or three degrees away from being truly orthogonal to the plane of the transparent layer). However, in other embodiments, the generally planar wavefront is provided at normal incidence and a beam splitter arrangement is used to separate the input and output optical paths. in the in 1 In the embodiment shown, the arrangement is such that light from the light source reflects off a mirrored backside of the SLM and interacts with a light modulating layer to form an output wavefront 112 . The output wavefront 112 is applied to optics with a Fourier transform lens 120 whose focal point is on a screen 125 . More specifically, Fourier transform lens 120 receives a beam of modulated light from SLM 140 and performs a frequency-to-space transform to produce a holographic reconstruction on screen 125 .

With this type of holography, each pixel of the hologram contributes to the overall reconstruction. There is no one-to-one correlation between specific points (or image pixels) on the display panel and specific light modulating elements (or hologram pixels). In other words, the modulated light leaving the light modulating layer is distributed over the entire display panel.

In these embodiments, the position of the holographic reconstruction in space is determined by the dioptric (focusing) power of the Fourier transform lens. in the in 1 embodiment shown, the Fourier transform lens is a physical lens. That is, the Fourier transform lens is an optical Fourier transform lens, and the Fourier transform is performed optically. Any lens can function as a Fourier transform lens, but the performance of the lens limits the accuracy of the Fourier transform it performs. Those skilled in the art know how to use a lens to perform an optical Fourier transform.

Gerchberg-Saxton method

In some embodiments, the computer generated hologram is a Fourier transform hologram, or simply a Fourier hologram or Fourier-based hologram, in which a far-field image is reconstructed by utilizing the Fourier transform properties of a positive lens. The Fourier hologram is calculated by Fourier transforming the desired light field in the display plane back into the lens plane. Computer generated Fourier holograms can be calculated using Fourier transforms.

A Fourier transform hologram can be calculated using an algorithm such as the Gerchberg-Saxton algorithm. In addition, the Gerchberg-Saxton algorithm can be used to compute a Fourier domain hologram (i.e., a Fourier transform hologram) from pure amplitude information in the spatial domain (e.g., a photograph). The phase information related to the object is effectively "fetched" from the pure amplitude information in the spatial domain. In some embodiments, a computer generated hologram is calculated from pure amplitude information using the Gerchberg-Saxton algorithm or a variant thereof.

The Gerchberg-Saxton algorithm assumes the situation that the intensity cross-sections of a light beam, I _A (x, y) and I _B (x, y), are known in planes A and B, respectively, and I _A (x, y ) and I _B (x, y) are related by a single Fourier transform. With the given intensity cross-sections, an approximation to the phase distribution in planes A and B, Ψ _A (x, y) and Ψ _B (x, y), is found. The Gerchberg-Saxton algorithm finds solutions to this problem through an iterative process. More specifically, the Gerchberg-Saxton algorithm iteratively applies spatial and spectral constraints while iterating a data set (amplitude and phase) representative of I _A (x,y) and I _B (x,y) between the spatial domain and the Fourier domain (spectral or frequency domain). The corresponding computer-generated hologram in the spectral domain is obtained by at least one iteration of the algorithm. The algorithm is convergent and is designed to produce a hologram representing an input image. The hologram can be a pure amplitude hologram, a pure phase hologram or a fully complex hologram.

In some embodiments, a pure phase hologram is calculated using an algorithm based on the Gerchberg-Saxton algorithm, as described in British Patent 2,498,170 or 2,501,112 which is hereby incorporated by reference in its entirety. However, the embodiments disclosed here describe the calculation of a pure phase hologram only by way of example. In these embodiments, the Gerchberg-Saxton algorithm extracts the phase information Ψ[u,v] of the Fourier transform of the data set resulting in known amplitude information T[x,y], where the amplitude information T[x,y] is representative of a Target image (e.g. a photograph) is. Because the Fourier transform combines amplitude and phase, the transformed amplitude and phase contain useful information about the accuracy of the computed data set. Therefore, the algorithm can be used iteratively with feedback of both amplitude and phase information. However, in these embodiments only the phase information Ψ[u,v] is used as a hologram to create a holographic image of the target image in an image plane. The hologram is a data set (e.g. a 2D array) of phase values.

In other embodiments, an algorithm based on the Gerchberg-Saxton algorithm is used to calculate a fully complex hologram. A fully complex hologram is a hologram with a magnitude component and a phase component. The hologram is a data set (e.g., a 2D array) that includes an array of complex data values, each complex data value including a magnitude component and a phase component.

In some embodiments, the algorithm operates on complex data and the Fourier transforms are complex Fourier transforms. Complex data can consist of (i) a real and an imaginary component or (ii) a magnitude component and a phase component. In some embodiments, the two components of the complex data are processed differently in different phases of the algorithm.

2A 12 shows the first iteration of an algorithm in accordance with some embodiments for computing a pure phase hologram. The input to the algorithm is an input image 210 comprising a 2D array of pixels or data values, where each pixel or data value is a magnitude or amplitude value.

That is, each pixel or data value of the input image 210 has no phase component. The input image 210 can therefore be viewed as a pure size, amplitude or intensity distribution. An example of such an input image 210 is a photo or a frame of a video that includes a temporal sequence of images. The first iteration of the algorithm begins with a data formation step 202A, which consists of assigning each pixel of the input image a random phase value using a random phase distribution (or random phase seed) 230 to form a complex output data set, where each data element of the set includes magnitude and phase. The complex output data set can be said to be representative of the input image in the spatial domain.

The first processing block 250 receives the output complex data set and performs a complex Fourier transform to form a Fourier transformed complex data set. The second processing block 253 receives the Fourier transformed complex data set and outputs a hologram 280A. In some embodiments, the hologram 280A is a pure phase hologram. In these embodiments, the second processing block 253 quantizes each phase value and sets each amplitude value to one to form the hologram 280A. Each phase value is quantized according to the phase levels that can be represented on the pixels of the spatial light modulator used to "display" the phase-only hologram. For example, if each pixel of the spatial light modulator provides 256 different phase levels, each phase value of the hologram is quantized into one phase level of the 256 possible phase levels. The hologram 280A is a pure phase Fourier hologram representative of an input image. In other embodiments, the hologram 280A is a fully complex hologram that includes a series of complex data values (each containing an amplitude and a phase component) derived from the received Fourier-transformed complex data set. In some embodiments, the second processing block 253 constrains each complex data value to one of a plurality of allowable complex modulation levels to form the hologram 280A. The step of constraining may include adjusting each complex data value to the closest allowable complex modulation depth in the complex plane. It can be said that the hologram 280A is representative of the input image im spectral, Fourier or frequency domain. In some embodiments, the algorithm stops at this point.

In other embodiments, however, the algorithm continues as indicated by the dashed arrow in FIG 2A shown. In other words, the steps following the dashed arrow in 2A follow are optional (ie, not essential to all embodiments).

The third processing block 256 receives the modified complex data set from the second processing block 253 and performs an inverse Fourier transform to form an inverse Fourier transformed complex data set. The inverse Fourier transformed complex data set can be said to be representative of the input image in the spatial domain.

The fourth processing block 259 receives the inverse Fourier transformed complex data set and extracts the distribution of amplitude values 211A and the distribution of phase values 213A. Optionally, the fourth processing block 259 evaluates the distribution of magnitude values 211A. In particular, the fourth processing block 259 may compare the distribution of magnitude values 211A of the inverse Fourier transformed complex data set with the input image 510, which is itself of course a distribution of magnitude values. If the difference between the distribution of magnitude values 211A and the input image 210 is sufficiently small, the fourth processing block 259 may determine that the hologram 280A is acceptable. That is, if the difference between the distribution of magnitude values 211A and the input image 210 is sufficiently small, the fourth processing block 259 may determine that the hologram 280A is a sufficiently accurate representative of the input image 210. In some embodiments, the distribution of the phase values 213A of the inverse Fourier transformed complex data set is ignored for comparison purposes. It is understood that any number of different methods of comparing the distribution of the magnitude values 211A and the input image 210 can be used and the present disclosure is not limited to any particular method. In some embodiments, a mean square difference is calculated and if the mean square difference is less than a threshold, the hologram 280A is considered acceptable. If the fourth processing block 259 determines that the hologram 280A is unacceptable, another iteration of the algorithm may be performed. However, this comparison step is not strictly required, and in other embodiments the number of iterations of the algorithm performed is predetermined or user-defined.

2 B shows a second iteration of the algorithm and all further iterations of the algorithm. The distribution of phase values 213A from the previous iteration is fed back through the processing blocks of the algorithm. The distribution of the magnitude values 211A is discarded in favor of the distribution of the magnitude values of the input image 210. In the first iteration, the data formation step 202A formed the first complex data set by combining the magnitude value distribution of the input image 210 with a random phase distribution 230 . However, in the second and subsequent iterations, the data formation step 202B involves the formation of a complex data set by combining (i) the distribution of phase values 213A from the previous iteration of the algorithm with (ii) the distribution of magnitude values of the input image 210.

The complex data set created by the data building step 202B of 2 B was formed, is then made in the same way as in 2A described to form the second iteration hologram 280B. The explanation of the process is therefore not repeated here. The algorithm may stop when the second iteration hologram 280B has been computed. However, any number of further iterations of the algorithm can be performed. It will be understood that the third processing block 256 is required only if the fourth processing block 259 is required or another iteration is required. The output hologram 280B generally gets better with each iteration. In practice, however, a point is usually reached where no measurable improvement can be observed, or the positive benefit of another iteration is outweighed by the negative effect of the additional processing time. Therefore, the algorithm is described as iterative and convergent.

$${\psi }_n\left[u,v\right]=\angle F\left\{\eta \cdot \text{exp}\left(i\angle R_n\left[x,y\right]\right)\right\}$$

$$\eta =T\left[x,y\right]-\alpha \left(\left|R_n\left[x,y\right]\right|-T\left[x,y\right]\right)$$

wo:

• F' ist die inverse Fourier-Transformation;
• F ist die Vorwärts-Fourier-Transformation;
• R[x, y] ist der vom dritten Verarbeitungsblock 256 ausgegebene komplexe Datensatz;
• T[x, y] ist das Eingabe- oder Zielbild;
• ∠ ist die Phasenkomponente;
• Ψ ist das Nur-Phasen-Hologramm 280B;
• ⍰ ist die neue Verteilung der Größenwerte 211B; und
• α ist der Verstärkungsfaktor.

2C Figure 12 shows an alternative embodiment of the second and subsequent iterations. The distribution of phase values 213A from the previous iteration is fed back into the processing blocks of the algorithm. The magnitude value distribution 211A is discarded in favor of an alternative magnitude value distribution. In this alternative embodiment, the alternative distribution of magnitude values is derived from the distribution of magnitude values 211 from the previous iteration. Specifically, the processing block 258 subtracts the magnitude value distribution of the input image 210 from the magnitude value distribution 211 of the previous iteration, scales this difference by a gain factor α, and subtracts the scaled one Difference from input image 210. This is expressed mathematically by the following equations, with the subscript text and numbers indicating the iteration number: $$R_{n+1}\left[x,y\right]=f\text{'}\left\{\text{ex}\left(i{\psi }_n\left[\mathrm{and},v\right]\right)\right\}$$

$${\psi }_n\left[\mathrm{and},v\right]=\angle f\left\{n\cdot \text{ex}\left(i\angle R_n\left[x,y\right]\right)\right\}$$

$$n=T\left[x,y\right]-a\left(\left|R_n\left[x,y\right]\right|-T\left[x,y\right]\right)$$

where:

• F' is the inverse Fourier transform;
• F is the forward Fourier transform;
• R[x,y] is the complex data set output from the third processing block 256;
• T[x,y] is the input or target image;
• ∠ is the phase component;
• Ψ is the phase-only hologram 280B;
• ⍰ is the new distribution of magnitude values 211B; and
• α is the gain factor.

The amplification factor α can be fixed or variable. In some embodiments, the gain factor ⍰ is determined based on the size and rate of the incoming target image data. In some embodiments, the amplification factor ⍰⍰is depends on the number of iterations. In some embodiments, the gain factor ⍰⍰is is solely a function of the number of iterations.

The embodiment of 2C otherwise corresponds to that of 2A and 2 B . One can say that the pure phase hologram Ψ(u,v) contains a phase distribution in the frequency or Fourier domain.

In some embodiments, the Fourier transform is performed using the spatial light modulator. Concretely, the hologram data is combined with second data indicative of the optical power. That is, the data written in the spatial light modulator includes hologram data representing the object and lens data representative of a lens. When displayed on a spatial light modulator and illuminated with light, the lens data emulates a physical lens, ie it brings the light into focus in the same way as the corresponding physical optics. So the lens data provides optical or focusing power. In these embodiments, the physical Fourier transform lens 120 can be made of 1 be omitted. It is known how to calculate the data representative of a lens. The data representative of a lens can be referred to as a software lens. For example, a pure phase lens can be formed by calculating the phase delay introduced by each point of the lens due to its index of refraction and its spatially varying optical path length. For example, the optical path length at the center of a convex lens is greater than the optical path length at the edges of the lens. A pure amplitude lens can be formed by a Fresnel zone plate. It is also known in the field of computer generated holography how to combine data representative of a lens with a hologram so that a Fourier transform of the hologram can be performed without requiring a physical Fourier lens. In some embodiments, the lens data is combined with the hologram by simple addition, e.g. B. by simple vector addition combined. In some cases, a physical lens is used in conjunction with a software lens to perform the Fourier transform. In other embodiments, the Fourier transform lens is omitted altogether so that the holographic reconstruction occurs in the far field. In further embodiments, the hologram can be combined with grating data in the same way, ie with data that the function of a grating, e.g. B. the image control take over. Here, too, it is known in practice how such data can be calculated. A pure phase grating can be formed, for example, by modeling the phase delay introduced by each point on the surface of a blazed grating. An amplitude-only grating can easily be overlaid with an amplitude-only hologram to allow angular control of the holographic reconstruction. The second data that provides for lens formation and/or control may be referred to as a light processing function or pattern to distinguish it from the hologram data, which may be referred to as an imaging function or pattern.

In some embodiments, the Fourier transform is performed jointly by a physical Fourier transform lens and a software lens. That is, part of the optical power that contributes to the Fourier transform is provided by a software lens, and the rest of the optical power that contributes to the Fourier transform is provided by physical optics or an optical system.

In some embodiments, a real-time engine is provided that acquires image data emp catches and calculates holograms in real time using the algorithm. In some embodiments, the image data is a video with a sequence of frames. In other embodiments, the holograms are precomputed, stored in computer memory, and retrieved for display on an SLM when needed. That is, in some embodiments, there is a memory with predetermined holograms.

The disclosed implementations relate to Fourier holography and the algorithms of the Gerchberg-Saxton type only by way of example. The present disclosure also applies to Fresnel holography and Fresnel holograms, which can be calculated using a similar method. The present disclosure is also applicable to holograms calculated using other techniques, e.g. B. with methods based on point clouds. As can be seen, a point cloud method for hologram calculation is described in the following figures. However, other methods of hologram calculation may also be used, including those referred to above in relation to the 2A until 2C described Fourier method can be used.

light modulation

A spatial light modulator can be used to display the diffraction pattern including the computer generated hologram. If the hologram is a pure phase hologram, a spatial light modulator that modulates the phase is required. If the hologram is a fully complex hologram, a spatial light modulator that modulates phase and amplitude can be used, or a first spatial light modulator that modulates phase and a second spatial light modulator that modulates amplitude can be used.

In some embodiments, the light modulating elements (i.e., the pixels) of the spatial light modulator are cells containing liquid crystals. That is, in some embodiments, the spatial light modulator is a liquid crystal device in which the optically active component is the liquid crystal. Each liquid crystal cell is configured to selectively provide a plurality of levels of light modulation. That is, each liquid crystal cell is configured to operate at a light modulation level selected from a plurality of possible light modulation levels at all times. Each liquid crystal cell can be dynamically reconfigured to a different light modulation level from the plurality of light modulation levels. In some embodiments, the spatial light modulator is a reflective liquid crystal-on-silicon (LCOS) spatial light modulator, but the present disclosure is not limited to this type of spatial light modulator.

An LCOS device provides a dense array of light modulating elements, or pixels, in a small aperture (e.g., a few centimeters wide). The pixels are typically around 10 microns or less, resulting in a diffraction angle of a few degrees, which means the optical system can be compact. It is easier to adequately illuminate the small aperture of an LCOS SLM than the larger aperture of other liquid crystal devices. An LCOS device is typically reflective, which means that the circuitry that drives the pixels of an LCOS SLM can be buried under the reflective surface. This leads to a higher aperture ratio. In other words, the pixels are densely packed, meaning there is very little dead space between pixels. This is advantageous because it reduces optical noise in the display panel. An LCOS SLM uses a silicon backplane, which has the advantage that the pixels are optically flat. This is particularly important for a phase modulating device.

A suitable LCOS-SLM is described below only by way of example with reference to 3 described. An LCOS device is fabricated from a single crystalline silicon substrate 302 . It has a 2D array of square planar aluminum electrodes 301 spaced apart by a gap 301a and placed on top of the substrate. Each of the electrodes 301 can be addressed via circuits 302a buried in the substrate 302 . Each of the electrodes forms a plane mirror. An alignment layer 303 is disposed on the electrode assembly, and a liquid crystal layer 304 is disposed on the alignment layer 303 . A second alignment layer 305 is formed on the planar transparent layer 306, e.g. B. made of glass arranged. A single transparent electrode 307, e.g. B. made of ITO, is arranged between the transparent layer 306 and the second alignment layer 305.

Each of the square electrodes 301, together with the overlying portion of the transparent electrode 307 and the liquid crystal material therebetween, defines a controllable phase modulating element 308, often referred to as a pixel. The effective pixel area or fill factor is the percentage of the total pixel that is optically active, taking into account the space between pixels 301a. By controlling the voltage applied to each electrode 301 with respect to the transparent electrode 307 the properties of the liquid crystal material of the respective phase modulation element can be varied in order to achieve a variable retardation of the light incident on it. The effect is a pure phase modulation of the wavefront, ie there is no amplitude effect.

The LCOS-SLM described outputs spatially modulated light in reflection. Reflective LCOS SLMs have the advantage that the signal lines, gate lines, and transistors are below the mirrored surface, resulting in high fill factors (typically over 90%) and high resolutions. Another advantage of using a reflective LCOS spatial light modulator is that the liquid crystal layer can be half the thickness of a transmissive device. This significantly improves the switching speed of the liquid crystal (a crucial advantage for projection of moving video images). However, the teachings of the present disclosure can also be implemented with a transmissive LCOS SLM.

Image projection with a small display device and a long viewing distance

The present disclosure relates to image projection where the distance between the display device and the viewer is much greater than the size of the display device. The viewing distance (i.e., the distance between the viewer and the display) may be at least an order of magnitude greater than the size of the display. The viewing distance can be at least two orders of magnitude greater than the size of the display device. For example, the pixel area of the display device may be 10 mm x 10 mm and the viewing distance 1 m. The image projected by the system is generated on a display plane that is spatially separated from the display device. The entrance aperture through which the viewer sees the image can also be relatively small compared to the viewing distance.

According to the present disclosure, the image is generated by holographic projection. A hologram is displayed on the display device. The hologram is illuminated by a light source (not shown) and an image is perceived on a display plane that is spatially separate from the hologram. The image can be real or virtual. For the following explanations, it is helpful to consider a virtual image that is created in front of the display device. That is, it appears behind the display device. However, it is not essential that the image is virtual and the present disclosure is also applicable to a real image formed between the display device and the viewing system.

The present disclosure allows a very small display device to be used to display images (real or virtual) even when the viewing distance is relatively large. It does this by providing a hologram that mimics the presence of the image in a desired location, and intelligently directing the light spatially modulated by that hologram, taking into account the location of the viewing system and the size and/or shape of the entrance aperture through which the light entering the viewing system must be taken into account.

The display device includes pixels that display the hologram. The pixel structure of the display device is diffractive. The size of the holographic image is therefore determined by the rules of diffraction. A consequence of the very small size of the display device is outlined below using 4 explained.

4 12 shows an aperture 402 that forms a small viewing window between a real object or image 401 and a viewing system 405. Bezel 402 is representative of the bezel of a display device. 4 illustrates the effect of the aperture 402 on the light coming from the real object or image 401 that is a finite distance in front of the aperture 402 . The aperture 402 is very small in relation to the distance between it and a viewing system 405. In this exemplary arrangement, the image 401, the display device 402 and the viewing system 405 are arranged on an optical axis Ax.

In 4 only those light rays (or bundles of rays) of the image 401 are shown which pass through the very small viewing window defined by the stop 402 and travel towards a viewing plane 406 defined perpendicular to the optical axis Ax. The skilled reader will understand that other rays of light emanate from image 401 but do not coincide with aperture 402, so they cannot reach viewing plane 406 (in this example). In addition, five rays of light (or bundles of rays) are shown emanating from image 401 - one from each of the five different parts of image 401 - but again the skilled reader will appreciate that this is illustrative only and does not cover the present disclosure is limited to five rays or bundles of rays. The viewing system 405 has an entrance aperture 404 located immediately in front of the viewing plane 406 . Viewing system 406 may be a human eye. The inlet opening 404 can therefore The pupil of the eye and the viewing plane 406 can be the retina of the eye.

4 Figure 12 illustrates how the very small size of the aperture 402 results in only a portion of the image being viewable from any position on a viewing plane. 4 shows the five example light beams, each characterized by a certain angle to the optical axis Ax and each emanating from a different part of the image 401. The light beam moving along the optical axis Ax carries the central part of the image, ie it is the light of the center of the image. The other light beams carry the other parts of the image. A consequence of the very small viewing window defined by the stop 402 and the very small entrance opening of the pupil 404 compared to the large viewing distances is that not all of the image content can pass through the entrance pupil 404 at any given viewing position. In other words: Not the entire image content is taken in by the eye. In the example of 4 only one of the five light beams shown passes the pupil 404 in each viewing position.

In this example, at the illustrated pupil position 404, the middle portion of the image is seen by the eye. The rest of the image information is blocked. The reader will understand that if the viewer moves up or down, a different beam of light may be received by the eye and e.g. B. the middle part of the image may be blocked. So the viewer sees only a part of the whole picture. The rest of the image information is blocked. In other words, the viewer's view is severely limited as he views the image through the small aperture of the display device itself.

In summary, the light propagates through a range of angles from the display device to the small viewing window. At a viewing distance of 1 m, only a small angular range of the small viewing window can propagate through the pupil of the eye to form an image on the retina at a given eye position. Only the parts of the image that are included in the in 4 shown small angular range that passes through the entrance opening 404. Accordingly, the field of view is very small, and the specific angular range is highly dependent on eye position.

This in 4 The problem of small field of view and sensitivity to eye position discussed above is a consequence of the long viewing distance and the small aperture of the viewing window and the small entrance aperture of the viewing system. The importance of viewing distance is discussed in the 5 until 7 explained in more detail.

It is known to use holograms that are displayed on a suitable display device and illuminated to create images (real or virtual) at a desired location. However, the present inventors have found that conventional holographic techniques are inadequate to produce an image clearly and accurately with a small display device, particularly at a relatively long viewing distance or with relatively small viewing apertures. They have further recognized that this is particularly the case when an image, e.g. B. a virtual image is to be displayed at a non-infinite distance from the viewer. Furthermore, the inventors have recognized that conventional holographic techniques typically rely on the formation of a holographic reconstruction of the image between the display device and the viewer, which holographic reconstruction can be formed in free space or in a photosensitive element. However, the formation of an intermediate holographic reconstruction typically requires additional optical elements such as diffusers, lenses, or mirrors, which may be impractical or otherwise undesirable, particularly in applications where compact design is desired and real estate value is high.

5A 12 shows a display device 502 arranged to display a hologram and to transmit light spatially modulated in accordance with the hologram to a viewing system comprising an entrance aperture 504 and a viewing plane 506. FIG. The display device in 5A has a similarly small physical size as the viewing port in 4 . In 5A Also visible upstream of the display device 502 is a light ray trace of a virtual image (not shown) representing the hologram. The virtual image 501 is at infinity, so the rays traced between the virtual image and the display device 502 are collimated. The collimated light from the virtual image is shown as consisting of five light rays or light beams, however, this is for illustration only and should not be taken as a limitation of the present disclosure.

The lower part of 5A shows an enlarged view of the vision system. This figure is schematic, which is why physiological details of the eye are not shown. In practice, of course, there is a light source (in 5A not shown) that illuminates the display device 502.

In 5A the distance between the display device and the viewing plane is so small that the full angle of diffraction of the light rays emanating from the display device forms the image on the retina the can. In other words, the light propagation paths of all five light beams (coming from the virtual image) pass through the entrance aperture. Accordingly, all points of the virtual image are mapped onto the retina and the entire image content is delivered to the viewing plane. So the field of view of the perceived image is maximum. In the optimal position, the field of view is equal to the diffraction angle of the display device. Interestingly, different pixels on the retina are formed by light propagating from different areas of the display device 502 - e.g. B. the pixel that is in 5A uppermost is formed by light propagating only from the lower part of the display device. Light propagating from other areas of the display device does not contribute to this pixel.

5B shows the situation that arises when the viewing distance is increased.

5B Figure 12 shows a display device 502' arranged to display a hologram and to transmit light modulated according to the hologram to a viewing system comprising an entrance aperture 504' and a viewing plane 506'. The virtual image 501' is at infinity, so the rays traced between the virtual image and the display device are collimated. The lower part of 5B shows an enlarged view of the vision system. This figure is schematic and therefore does not show physiological details of the eye. In practice, of course, there is a light source (in 5B not shown), which is used to illuminate the display device 502'.

5B shows only the rays of light that can propagate through aperture 504'; all other rays that cannot pass through aperture 504' are omitted. However, it goes without saying that these other rays would also propagate from the display device 502'. At the larger viewing distance of 5B the cone of light has spread so far in the viewing plane that some of the ray bundles are blocked by (ie, not physically coincident with) the entrance aperture 504'. In this example, in particular, the bundles of rays associated with the edge regions of the virtual image are blocked by the entrance pupil 504'. However, if the entrance aperture 504' is translated parallel to the viewing plane 506', different beams of rays may coincide with the aperture 504' so that different portions of the virtual image would be seen. Accordingly, the entire virtual image is not visible for a given position of the aperture, and the visible part of the virtual image depends strongly on the position of the aperture (e.g. the eye). Therefore, large distances between the display device and the viewing system are problematic due to the small size of the display device, particularly in conjunction with a relatively small entrance aperture.

6A 12 shows an improved system having a display device 602 that propagates light encoded with a hologram displayed on the display device 602 toward a viewing system that includes an entrance aperture 604 and a viewing plane 606. FIG. In practice, of course, there is a light source (not shown) arranged to illuminate the display device 602 . The improved system further includes a waveguide 608 positioned between the display device 602 and the entrance aperture 604 . The lower part of 6A 12 shows an enlarged view of the entrance pupil 604 and the viewing plane 604. This figure is schematic and therefore does not show physiological details of the eye.

The viewing distance in 6 is the same as in 5B . However, the in 5B The blocked beam is effectively restored by the waveguide 608 so that the full image information is received by the viewing system - despite the longer viewing distance.

The presence of the waveguide 608 allows the full angular content of the display 602 to be received by the eye, even at this relatively large throw distance. This is because the waveguide 608 acts as a pupil dilator in a manner that is well known and will therefore only be described briefly here.

Briefly, the waveguide 608 consists of a generally elongate structure. In this example it consists of an optical slab of refractive material, but other types of waveguides are known and can be used. The waveguide 608 is arranged to intersect the cone of light projected from the display device 602, for example at an oblique angle. The size, location and position of the waveguide 608 are designed so that the light from each of the five beams enters the waveguide 608 within the cone of light. The light from the light cone enters the waveguide 608 via its first planar surface 610 (closest to the display 602) and is guided at least partially down the length of the waveguide 608 before passing over its second planar surface 612, that of the first Area 610 (closest to the eye) substantially opposite, is radiated. Of course, the second planar surface 612 is partially reflective and partially transmissive. In other words, as each ray of light travels within the waveguide 608 from the first planar surface 610 to the second planar surface 612 of the waveguide 608, some of the light is let out of the waveguide 608 and some from the second planar surface 612 back to the first planar Surface 610 reflected. The first planar surface 610 is reflective such that any light striking it from the waveguide 608 is reflected back to the second planar surface 612 . Therefore, some light may simply be refracted between the two flat surfaces 610, 612 of the waveguide 608 before being transmitted, while other light may be reflected and thus cause one or more reflections (or "bounces") between the flat surfaces 610, 612 of the waveguide 608 can be experienced before it is transmitted. A net effect of the waveguide 608 is therefore that the transmission of the light is effectively extended over multiple locations on the second planar surface 612 of the waveguide 608 . The total angular content output by the display device 602 can thus be present at a greater number of positions on the display plane (and at a greater number of positions on the aperture plane) than would be the case without the waveguide 608 . This means that light from each ray bundle can enter the input aperture 604 and contribute to an image formed by the viewing plane 606 despite the relatively large projection distance. In other words, the entire angular content of the display device 602 can be received by the eye. Thus, the full diffraction angle of the display device 602 is utilized and the viewing window for the user is maximized. This in turn means that all light rays contribute to the perceived virtual image 601 .

6B shows the individual optical paths for each of the five bundles of rays leading to five corresponding pixels within the virtual image 601 6A contribute - labeled R1 to R5 from top to bottom. As can be seen, the light from R1 and R2 is simply refracted and then transmitted through the waveguide 608. The light from R4, on the other hand, is refracted only once before being transmitted. The light from R3 includes a portion of the light from a corresponding first portion of the display 602 that is simply refracted by the waveguide 608 before being transmitted, and a portion of the light from a second, different corresponding portion of the display 602 that is before of transmission encounters a single bounce. Similarly, the light from R5 includes some light from a corresponding first portion of indicator 602 encountering a single bounce prior to transmission and a portion of light from a second, different corresponding portion of indicator 602 encountering prior to transmission Transmission hits two rebounds. For each of the regions R3 and R5, two different parts of the LCOS propagate the light corresponding to that part of the virtual image.

The inventors have recognized that in at least some applications it is advantageous if the distance of the virtual image - i. H. the distance between the viewer and the virtual image - is finite, in contrast to a virtual image that is created at infinity. In certain applications, there is a preferred virtual image distance at which it is desirable or necessary for the virtual image content to appear.

This can e.g. B. be the case with a head-up display, z. B. in the automotive field, if the virtual image content is to be overlaid on the real content that is seen by the viewer through the windshield of the vehicle. A desired virtual image distance can consist, for example, in the virtual image content being formed a few meters, for example 3 meters or 5 meters, in front of the viewer's vehicle or windshield.

The upper part of 7 12 shows a system having a display device 702 that propagates light 703 encoded (ie, appropriately modulated) with a hologram displayed on the display device 702 toward an eye having an entrance aperture 704 and a viewing plane 706. There is a light source (not shown) arranged to illuminate the display device 702 . The system further includes a waveguide 708 disposed between the display device 702 and the entrance aperture 704 to act as a pupil dilator, as referred to above in relation to FIG 6a described in detail. The middle part of 7 12 shows an enlarged view of the entrance aperture 704 and the viewing plane 706, and the bottom part of FIG 7 FIG. 7 shows another enlarged view of the viewing plane 706. This figure is schematic and therefore does not show physiological details of the eye. With this arrangement, the eye perceives the virtual image 701 as being a finite distance in front of the display device 702 . The light rays are divergent because the distance of the virtual image is finite.

As in 6A shown, allows for the presence of waveguide 708 in 7 access to the full diffraction angle of the display device 702 at a relatively large projection distance, so that the entire image content for the user is visible at the viewing position shown.

However, another technical problem arises. Due to the divergent light and the resulting different light beam angles, the different optical paths of the light from different parts of the display device 702 for certain bundles of rays can result in these bundles of rays each forming several pixels on the retina 706 when the virtual image is at a finite virtual image distance is formed. This is in relation to the ray bundles denoted R3' and R5' in 7a shown. The additional pixels formed which are subordinate to a main pixel for a particular point within the virtual image may be referred to as "ghost pixels" and together they form "ghosts" or simply "ghosts". As those skilled in the art know, ghosting can result in blurring and an overall degradation in the perceived quality of a virtual image from the viewer's perspective. This is especially true when the "ghost" images partially overlap the "main" image.

8th shows an example of a virtual image of the numbers "5" and "9" obtained with a similar viewing system as in 7a was created and contains ghost images in addition to a main image. The main image is seen as the brightest, central image for each number, with ghosting left and right. In the example of 8th The "9" is created when the viewing distance is greater than that of the "5", which is why the blurriness is more pronounced with it.

Hologram calculation - example 1

The inventors have addressed the problem of ghosting. The inventors have recognized that it is desirable to provide a viewing system in which a virtual image can be formed at a finite virtual image distance that encompasses all angular image content output from a display device and that reduces or eliminates ghosting . In addition, the inventors have found that the larger a viewing aperture in a conventional viewing system, the greater the risk of ghosting because the aperture may transmit additional rays of light that may form additional pixels on the display plane. Therefore, it is desirable to provide an improved viewing system that can accommodate apertures of different sizes while still reducing or eliminating ghosting. The solutions provided by the inventors, which are discussed in more detail below, are applicable to a variety of different sizes and configurations of iris, waveguide and display device and can be used for different propagation distances at which one or more ghost images can typically arise. In addition, they can be applied to relatively small display devices.

In summary, the inventors have recognized that it is possible to provide a light engine for generating a hologram that avoids or reduces ghosting when the hologram is displayed on the display device and illuminated while the full image can be viewed closely. The inventors have further recognized that it is possible to provide a hologram engine for providing such a hologram and to provide an improved viewing system for displaying and illuminating an improved hologram to produce enhanced images even when the projection distances in the viewing system are relatively large and the display device and/or the viewing aperture is relatively small.

According to a disclosed embodiment, the inventors have found that the hologram can be modeled using a modeling method such as e.g. B. a ray tracing method such. B. a point cloud hologram computation technique, can be determined. Indeed, the modeling as developed by the present inventors identifies one or more areas of a display device that in a conventional arrangement would contribute to one or more ghost images, and the hologram is derived to account for the contributions from those one or more to control areas of the display device and thus avoid or reduce the formation of ghost pixels when the hologram is displayed and illuminated on the display device.

Other approaches to determining the hologram are also disclosed herein, as described below with respect to subsequent figures.

The inventors have recognized that due to the angular limitations resulting from a viewing system incorporating a waveguide such as that shown in FIGS 6A and 7A shown - with a relatively small viewing aperture and optionally also a relatively small display device, it is possible to consider separately the different possible propagation paths within the waveguide. In addition, the inventors have recognized that as a result of such viewing is possible to identify each of the following areas: areas of the display device that are the light source contributing to a desired "main"image; Areas of the display that are the light source contributing to an undesirable "ghost"image; and areas of the display device that are the light source that is blocked by the bezel and therefore does not contribute to either the main or ghost image. The inventors have further recognized that it is possible to limit the hologram calculation to only those areas of the display device that contribute to the main image. The inventors have further recognized that in a further improvement, in some embodiments, an improved hologram can be provided that causes one or more of the ghost images to be translated to be overlaid on a main image.

The disclosed discoveries, and the improved systems and methods that embody those discoveries, may be better understood with reference to the figures described below.

9A Figure 9 shows a display device 902, which in this example is an LCOS spatial light modulator. The term "LCOS" is used below as an abbreviation for "display device". The teachings of the present disclosure are not limited to an LCOS display device. 9B 12 shows the LCOS 902 and traces the light rays with respect to a virtual pixel from the LCOS 902 via a waveguide 908 towards a viewing unit/system 905, which in this example comprises an eye of the viewer. 9C Figure 9 shows an enlarged view of the eye 905 showing the rays at the pupil 904 (ie the entrance aperture) and the retina 906 (ie the sensor or viewing plane). In this example, the entire LCOS region contributes to the formation of the pixel on the retina 906. In other words, the entirety of the LCOS 902 is "visible" to the viewer. This contribution of the entire LCOS 902 to the image is illustrated by the entire LCOS area being hatched, indicating its entire surface as a "contributing area".

As in the 9B and 9C As can be seen, the light tracked by the LCOS 902 results in the formation of three pixels - labeled G1, M, and G2 respectively - on the retina 906 for that particular virtual pixel. The center pixel "M" is a main pixel that contributes to the virtual primary/main image as perceived by the viewer. The top pixel G1 includes a first ghost pixel and the bottom pixel G2 includes a second, different ghost pixel of the same virtual pixel. In particular, the inventors have recognized that it is possible to identify the area or areas of the LCOS 902 that contribute to the main pixel M and/or to the ghost pixels G1, G2.

The 10A until 10C show the LCOS 902 and the ray diagram of FIG 9A until 9C , divided into three propagation paths each, the first of which includes the light contributing to the lower ghost pixel G2, the second the light contributing to the main pixel M, and the third the light contributing to the upper ghost pixel G1. As in 10A As can be seen, the light contributing to G2 is reflected three times before being transmitted through waveguide 908. As in 10B As can be seen, the light contributing to M is redirected twice before being transmitted through waveguide 908. As in 10C As can be seen, the light contributing to G1 is redirected once before being transmitted through waveguide 908.

Also in each figure (10A, 10B, 10C) the areas of the LCOS 902 that contribute to each pixel are shaded. Thus, it can be seen that the lower ghost pixel G2 is influenced by an area in the lower part of the LCOS 902, the upper ghost pixel G1 by an area in the upper part of the LCOS 902, and the main pixel by the entire LCOS 902.

The aperture 904 (ie the viewer's pupil) is in the example 9A until 9C and 10A until 10C relatively large, which explains why the entire LCOS 902 contributes to the main pixel. In other words, the f-number of the viewing system is relatively low in this example. The 10A until 10C show that while portions of the LCOS 902 also contribute to one or the other ghost G1, G2, there is a portion of the LCOS 902 that does not contribute to either ghost G1, G2, only the main pixel M. The inventors have recognized that this area can be identified as a contributing area for the LCOS 902 in this example - more specifically, it can be identified as a "primary contributing area" as will become more apparent from the description of the figures below. It can therefore be seen in this case that the primary contribution area is not limited to a circle or an ellipse and can also take on other, more complex shapes.

The 11A until 11C show the corresponding ray diagrams for different points of the virtual image when the entrance aperture is relatively small (ie, the f-number is relatively high). 11A refers to a first field point of the virtual image (ie a first point of the virtual image), 11B to a second field point of the virtual image and 11C to a third field point of the virtual image. The 11A until 11C show that not all of the LCOS 902 contributes to the main pixel. Rather, they show 11A until 11C that a first area of the LCOS corresponds to the main pixels (referred to herein as "primary contributing area") and a second area of the LCOS corresponds to ghost pixels (referred to herein as "secondary contributing area").

The inventors have recognized that under certain conditions, different areas of the LCOS 902 (or other display device in a viewing system) contribute to either a main image, a ghost image, or no visible portion of an image. They have also recognized that the hologram determination process can be optimized using this information. For example, the light from certain parts of the display can be omitted, or in some cases the way in which those parts of the display are encoded by the hologram can be changed so that they contribute positively to the main image rather than a ghost image to contribute. In addition, additional areas of the display device can be identified that can be configured to make a positive contribution to the main image.

The detections made by the inventors are described below by way of example in relation to point cloud holograms. However, they can also be applied to other types of holograms, such as e.g. B. a Fourier or Fresnel hologram, as will be explained in more detail with reference to the following figures in the further course of this disclosure. That is, other hologram calculation methods may be optimized according to the inventors' findings as set forth in this disclosure.

As is well known, for the calculation of a point cloud hologram of an image (e.g. a virtual image), the image is usually broken down into (i.e. represented by) a large number of individual points, which are referred to here as "virtual points" since we use the Describe formation of virtual images. A spherical wave (or "wavelet") is then computed - i. H. using a model or other theoretical tool - from each virtual point at its intended or desired location within the virtual image - to the plane of the display device - such as the plane of the LCOS in the examples described above. The manner in which such wavelets would interfere with each other is considered and the resultant amplitude and/or phase of the wavelet that would be received at each pixel of the display device is calculated. The display device can then be adjusted, in a manner known and not further described here, to have the amplitude and/or phase modulation required at each pixel to mimic the calculated wavelets and so produce a hologram of the image.

The inventors have recognized that in a single waveguide viewing system with a long viewing distance as described herein, when the entire display device is filled with the net amplitude and phase of the corresponding wavelets of all virtual points, the resulting hologram when displayed and illuminated is a or can produce multiple ghost images as well as one main image. This can be particularly the case when the viewing system is configured to view a virtual image at a finite distance from the viewer. In addition, in many cases light rays emitted by pixels in some parts of the device are wasted (i.e. do not contribute to the image that the viewer sees or perceives) because the physical limitations of the viewing system (e.g. a small aperture and/or a small display device and/or a long throw distance) prevent the light from these parts of the device from reaching the viewer's eye. Therefore, the inventors have recognized that an intelligent selection can be made as to which parts of the display device are adjusted in such a way that a hologram is produced. In particular, if only those sections (or portions or regions) of the LCOS are selected that contribute to a main image - and if wavelets are computationally propagated only from the virtual points of the intended virtual image to those sections of the LCOS - and not to other sections of the LCOS that do not contribute to the main image - the resultant amplitude and/or phase of the wavelet that would be received at each pixel within the selected area of the display device can be calculated. No calculation is required for all other parts of the indicator.

The display device can then be adjusted in accordance with the improved calculation to have the amplitude and phase modulation required at each pixel position within the selected section(s) to mimic the calculated wavelets and thus a hologram of the main image to create. When this is done there is no need to change other parts of the LCOS and therefore no image information is transmitted from these other parts to the viewer's eye (or other viewing entity) when the calculated hologram is displayed and illuminated on the display device. Therefore, no information is available to the viewer which could lead to the formation of an unwanted "ghost" pixel. As a result, the ghost point(s) will be eliminated or "erased". In addition, no computational or image information is wasted, as only those pixels of the display device are adjusted that are known to provide light passing through the viewer's pupil (or through the aperture of a corresponding other viewing unit) for a given set of Conditions (z. B. for a certain opening width and position of the eye) is admitted.

12A FIG. 12 shows a system 1200 that generates a virtual image with an exemplary virtual point 1201. FIG. Viewing system 1200 includes a display device 1202, which in this example is an LCOS SLM, including a contributing region 1203 and a non-contributing region 1207 identified in accordance with the present disclosure. The display device 1202 is arranged to display a hologram of the virtual image and to project light encoded according to the hologram towards an eye 1205 which has a pupil (not shown) serving as an aperture, a lens 1209 and a Retina 1206 serving as the viewing plane. The lens 1209 and retina are separated by a separation distance "A". There is a light source (not shown) arranged to illuminate the display device 1202 . The viewing system 1200 further includes a waveguide 1208 disposed between the LCOS 1202 and the eye 1205 . This figure is schematic, therefore physiological details of the eye are not shown.

Virtual point 1201 is upstream of display device 1202, which is shown in 12A represented by the virtual point 1201 being to the left of the display device 1202. The virtual point 1201 has a location defined by spatial coordinates, which in this example include Cartesian (x,y,z) coordinates, but other coordinate systems or other means of identifying the location of the virtual point may be used. A distance "z" is defined between the virtual point 1201 and the display device 1202 in a direction substantially parallel to the optical axis of the display device 1202 . In addition, a distance "I" is defined between the display device 1201 and the eye lens 1209 , which runs essentially parallel to the optical axis of the display device 1201 . The numerical values of "z" and "I" will vary depending on the particular placement of the vision system 1200 at any given time, including the position of the viewer. For example, the display-to-lens distance "I" may be on the order of about 1 meter and the display-to-image distance "z" may be larger, for example on the order of a few meters. However, these numerical examples are for illustrative purposes only and are not to be considered as limiting.

The inventors have recognized that when a virtual image comprising the virtual pixel 1201 is viewed by a viewer at the in 12 the position shown is to be perceived, a corresponding pixel 1211 must be formed on the retina 1206. Rays of light can be traced from the virtual point 1201 of the virtual image via the LCOS 1202 to a corresponding point 1211 on the retina 1211 .

It is clear that more than one possible optical path can be taken between the virtual point 1201 and the corresponding point 1211 on the retina via the LCOS 1202 due to the possible paths created by the waveguide 1208. According to embodiments, a main light ray may be determined comprising one of a plurality of light ray paths between the virtual image point 1201 and the corresponding point 1211 on the viewing plane (i.e. the retina 1206). When this main ray path is identified, the number of deflections that the light of the main ray undergoes within the waveguide is determined. This number of bounces (B) can be defined as the number of bounces for which rays are to be traced between the virtual image and the viewing plane. In certain embodiments, the main jet—and the associated number (B) of rebounds—can be determined first.

In the present example, ray tracing can determine the part of the LCOS 1202 through which the "principal ray" passes between the virtual pixel 1201 and the corresponding point 1211 on the retina to determine the "contributing area" 1203 for that virtual pixel 1201. In 12 therefore, a ray of light “r” is shown propagating between the virtual pixel 1201 and the contributing area 1203 of the display device 1202. FIG. According to the findings of the inventors, from the virtual pixel 1201 and the display device 1202 only those wavelets are modeled (or otherwise computationally considered) that contribute to the contributing region of the LCOS. In other words, only the identified contributing area 1203 of the display device 1202 needs to be encoded (or “tuned”) to create an appropriate hologram. Such a hologram, encoded on the display device and appropriately illuminated, would allow the virtual pixel 1201 to be perceived by the viewer without ghost images of that virtual pixel 1201 also being present. This can be done using the 13 and 14 , which will be discussed below, better understand.

The contributory area 1203 in 12B - and the contributory areas below in relation to the 13 and 14 discussed - can be arranged in accordance with the intersection of the main ray with the display device. For example, the taxable area may be centered around the point where the chief ray intersects the display device. The size and shape of the contributing region can be determined based on the size and shape of the entrance aperture of the relevant display device and associated optics (e.g., waveguide geometry, any reflections within a larger optical system, etc.). When the viewing entity is a human eye, the associated area on the display device may in some cases be substantially circular or elliptical in shape, or some other suitable shape, e.g. B. have a complex shape with a similar size as the receiving pupil. However, the present disclosure also encompasses more complex shapes for the contributing region. The diameter of the pupil of the eye can be measured or estimated in any suitable way. The measurement of the pupil diameter can be carried out with an eye tracking system, for example. Alternatively, it can be estimated based on known ranges of the eye's pupil diameter (e.g. 2-6mm) or based on some other estimate taking into account the ambient light conditions at a given point in time.

The contributing area can be set to intentionally contribute to an area (on the aperture plane) that is slightly larger than the pupil and/or to an area (on the aperture plane) that has a slightly different shape than the pupil ( or another aperture). In such a case, not all of the light from a "contributing area" can pass through the pupil at all times, but the eye can move a little while still collecting enough light to form a good image on the retina.

13 FIG. 10 shows a method for determining the contributing and non-contributing areas of the display device, according to an aspect of this disclosure. Optionally, these determinations can then be used to guide the creation of one or more holograms for display and illumination by a viewing system such as system 1200 of FIG 12 to optimize. At the in 13 In the methods disclosed, the viewing system includes a lens with an “f” number (ie, focal length and aperture) and a camera. The light-sensitive component of the camera can, for. B. be a CCD line and is placed in the viewing plane. The lens and camera functionally replace the eye lens and retina of a viewer's human eye and are used solely in the process of determining the contributing and non-contributing areas of the display device. These areas of the display device can be determined for a multiplicity of viewing positions (e.g. eye positions within an eye-motion box) and/or a multiplicity of image distances (e.g. virtual image distances in front of a vehicle). In some ways that can in 13 The methods presented can be regarded as precursors of hologram calculation. The procedure can be seen as an optimization or even a calibration process.

Of course, each virtual image to be created can be represented by one or more virtual pixels, each having a corresponding location, e.g. B. is defined by (x,y,z) coordinates. Steps one 1302 through six 1312 (discussed in more detail below) of the method 1300 of FIG 13 can be applied separately to each virtual pixel within a virtual image to be created. In addition, the method 1300 applies to a specific set of conditions - ie, specific measurements and constraints - of the viewing system. Therefore, any iteration (or "run") of method 1300 for the construction of a particular image to be rendered (virtual pixel by virtual pixel) and in the event that the system has a particular display-image distance "z", has a certain distance "d" between the display device and the retina, a certain aperture width (pupil) and a certain virtual image distance at which the eye is focused. An iteration of the method 1300 is also specific to a particular size and type of display device and to a particular position of the eye with an allowable viewing window. There may be other measurements and/or constraints for which each iteration of the method is specific fish is. If any of these measurements or constraints change, the method 1300 may be re-performed to re-determine the contributing area(s) of the display under the changed circumstances. However, it should be understood that, according to embodiments, certain tolerances may be applied to one or more of these measurements or constraints such that the method need not be re-performed if they differ by less than a predetermined amount and/or for less than a predetermined length of time change. The rules for when the method should be repeated can be set individually for each system.

Method 1300 may be performed by any suitable processor. The processor may comprise, be included in, or be in communication with a hologram engine. The processor or the hologram module can be contained in a light module.

The processor may obtain or receive edge information about the viewing system prior to performing method 1300 . For example, it may obtain or receive information about the size of components such as the display device, information about the absolute and/or relative positions of various components and the viewing system (e.g., the potential human viewer), information about the light source, and so on.

According to the method 1300, in a first step 1302 the location - e.g. B. the coordinates [ _xvirtual , _yvirtual , _zvirtual ] - of the virtual image point (here also referred to as "virtual point" for short) is determined, which corresponds to the location at which the virtual image is to be perceived. Then the distance of the virtual image between the lens 1209 and the virtual point is ascertained or determined. This virtual image distance may be set or determined by the processor performing method 1300, or may be set or determined by another entity and communicated to that processor. In some arrangements it can be preset or selected from a variety of possible virtual image distances. In real operation, when the viewing system is an eye, eye or head tracking information can be used in determining the virtual image distance.

In a second step 1304, the required distance "A" between the lens and the sensor for focusing on the virtual pixel is determined. Each virtual pixel can also be defined by an angle - see 4 . The term “angular content” here refers to the virtual pixels of the virtual image.

In a third step 1306, a number of light reflections or bounces "B" within the waveguide associated with a main or primary image produced by the viewing system is determined. Those skilled in the art of optics will understand that the waveguide creates a variety of replicas of the light associated with the virtual pixel, and each replica may be associated with a different number of light reflections within the waveguide. For example, one way to determine B is to determine the intersection point of the chief ray with the display for each possible light propagation path in the waveguide and choose the number of reflections/bouncing that brings the chief ray closest to the center of the display. Advantageously, with this approach, the area of the display device that contributes to the vision system is the largest.

• 1. die Augenposition ist bekannt und wird als Eingabe verwendet Strahlengang von der Mitte des Anzeigegeräts zur ermittelten Augenposition für eine erste Anzahl von Bounces, B. Die Extrapolation dieses Strahls in Richtung des virtuellen Bildes definiert einen Winkel im Sichtfeld (θ_B) für diese Anzahl von Bounces (B).
• 3) Strahlenverlauf vom Zentrum des Anzeigegeräts zur ermittelten Augenposition für eine zweite Anzahl von Bounces, B+1. Die Extrapolation dieses Strahls in Richtung des virtuellen Bildes definiert einen Winkel im Sichtfeld (θ_B+1) für diese Anzahl von Rücksprüngen (B+1).
• 4. B ist die Anzahl der für den Winkelinhalt verwendeten Bounces zwischen θ_B und θ_B + (θ_B+1 - 0_B)/2
• 5. B+1 ist die Anzahl der für den Winkelinhalt verwendeten Bounces zwischen θ_B + (θ_B+1 - θ_B)/2 und θ_B

Another way to calculate the number of bounces to use in the third step 1306 is to use substeps 1 through 5 below:

• 1. the eye position is known and is used as input Ray path from the center of the display device to the determined eye position for a first number of bounces, B. Extrapolating this ray towards the virtual image defines an angle in the field of view (θ _B ) for that number of bounces (B).
• 3) Ray path from the center of the display device to the detected eye position for a second number of bounces, B+1. The extrapolation of this ray in the direction of the virtual image defines an angle in the field of view (θ _B+1 ) for that number of returns (B+1).
• 4. B is the number of bounces used for angular content between θ _B and θ _B + (θ _B+1 - 0 _B )/2
• 5. B+1 is the number of bounces used for angular content between θ _B + (θ _B+1 - θ _B )/2 and θ _B

The output of the first step 1302 (ie the coordinates of the virtual pixel) and the third step 1306 (the parameter B) are used in a fourth step 1308 to calculate the corresponding image position/pixel on the sensor [ _xsensor , _ysensor , _zsensor ] to determine. That is, the fourth step 1308 determines the point on the sensor at which the light of the virtual pixel is received. With in other words, the point on the sensor where the virtual pixel is imaged. This point on the sensor is referred to below 14 referred to as the main pixel [ _xsensor , _ysensor , _zsensor ]. For example only, computational ray tracing from the virtual point to the sensor can be used for B-bounces within the waveguide, but the present disclosure is not limited to this fourth step approach.

Those skilled in the art will understand that a main light ray (or simply main ray) can be identified from the virtual point [ _xvirtual , _yvirtual , _zvirtual ] to the point on the sensor [ _xsensor , _ysensor , _zsensor ]. Again, computational ray tracing can be used to identify or track the main ray, but other methods are also applicable. In a fifth step 1310, a display intersection [x _LCOS (B), y _LCOS (B), z _LCOS (B)] is identified, where the intersection of the display is the location on the display where the chief ray intersects the display . The point of intersection of the display device can be determined, calculated or measured, e.g. B. by computer-aided ray tracing.

In a sixth step 1312, a portion of the display associated with the intersection of the display [x _LCOS (B), y _LCOS (B), z _LCOS (B)] is identified. The area of the display device can be geometrically centered on this point [x _LCOS (B), y _LCOS (B), z _LCOS (B)]. The area can be a circle or an ellipse, for example, but other, more complex shapes are also conceivable. If the area is a regular shape such as a circle or an ellipse, the radius of the area can be specified, e.g. B. depending on the f-number of the lens of the viewing system. The surface is referred to herein as the "primary contributing surface" because it corresponds to a primary image produced by the viewing system. The word "contributing" means that the pixels of the display device within the identified area of the display device are the pixels that provide the necessary information content for the sensor. Other areas of the display device (ie other pixels of the display device) do not contribute to the formation of the pixel on the sensor. Of course, the other pixels can contribute to other pixels on the sensor that are associated with other virtual pixels.

The method according to the main aspect of the present disclosure ends with the determination of the primary contributing area of the display device. Optionally, a hologram can be determined based on the primary contributing area - rather than the entire area of the display device.

Accordingly, in an optional seventh step 1314, a hologram component for the primary contributing area is determined based on the virtual point. In particular, light parameters are determined for the primary contributing surface. The light parameters can be amplitude and/or phase for each pixel of the primary contributing area. For example, light amplitude and phase for each pixel within the primary contributing area can be determined based on the propagation of the light from the virtual point to the primary contributing area using a point cloud method known to those skilled in the art. The hologram component for the virtual point can be stored and combined with the hologram component for the other virtual points as part of the iterative process described in the following section to create a complete hologram for the entire virtual image.

In the seventh step 1314, a light modulation value (e.g., an amplitude and/or phase value) is assigned to each pixel value of the display device within the primary contribution region. This is achieved by considering the propagation of a lightwave from [ _xvirtual , _yvirtual , _zvirtual ] to the primary contributing region and measuring the amplitude and/or phase to the pixels of the display device within the desired radius of [x _LCOS (B), y _LCOS ( B), z _LCOS (B)] is added. That is, the amplitude and/or phase of the light emanating from the virtual image point and arriving at each point (i.e. pixel) of the primary contribution area is determined taking into account the propagation of the lightwave - i.e. the amplitude and/or phase of the lightwave after travel the distance from the virtual picture point to each pixel. This determination can be made by any number of different techniques known to those skilled in the optical arts. This determination can be made by experimental measurement.

The first through seventh steps can be repeated for each virtual point within a virtual image to be projected with the hologram. For example, the plurality of hologram components can be added to create a resulting hologram for each pixel of the display device. For example, the complex amplitude at each pixel can be added for propagation from all virtual pixels. If the hologram is to be displayed on a pure phase modulator, the amplitude component of the resulting complex amplitude the sum can be ignored, leaving only the phase. More generally, the result is a diffractive structure that corresponds to the virtual image and that when displayed and illuminated on the display device in the viewing system forms the virtual image.

The hologram can be displayed on the display device or encoded. This sets the display device to modulate the light so that the viewer can see the virtual image at the desired distance.

The method 1300 can be performed substantially simultaneously (or in very rapid succession) for each of a plurality of virtual points within a virtual image, such that an appropriate hologram for the entire virtual image can be derived and encoded on the display device very quickly, viz for a given viewing setting and for certain numerical measurements and constraints. If anything changes that could affect the identification of the contributing areas and/or the required adjustment of the display device, the method can be performed again. The processor may be configured to repeat the method in a timed loop and/or in response to a signal indicating that a change has occurred and/or when the content or identity of the required virtual image changes performs. The processor may include or be in communication with memory to store previously computed data. For example, a look-up table or other storage means may be provided that specifies the active area(s) of the display device for a particular virtual image or point under a particular set of measurements and/or constraints.

The method 1300 can be performed (or repeated) very quickly to display a series of different virtual images in quick succession and/or to accurately respond to changes in conditions, such as weather conditions. B. the movement of the user to react. Although in the system of 12 only one eye is shown, the method 1300 can be configured to accommodate both eyes of the viewer and/or another viewing system with two or more entrance apertures. Although some of the above descriptions refer to aperture width, it will be understood that a pupil (and most other sight apertures) is two-dimensional and can change size in either of these two dimensions. The method 1300 can be configured to take into account the two-dimensional aperture size and its changes.

The inventors found that a virtual image hologram with the reference to FIG 13 disclosed method could be efficiently determined. However, the inventors also found that in some cases only a relatively small portion of the LCOS was used, if not all areas of the LCOS that would conventionally propagate light that would ghost form were used. In a notable technical advance, the inventors found ways to utilize additional areas of the LCOS, in addition to the primary contributing area, and to calculate hologram values for these additional areas that would allow them to contribute light to enhance the primary image instead form unwanted ghost images.

As is well known, the optical path taken by a ray of light through a waveguide in a viewing system can increase its path length over the path lengths for the corresponding other rays. Typically, such magnifications are likely to be small compared to the virtual image distance "v" and therefore not visible to the eye.

14 FIG. 14 shows an even further improved method 1400 based on additional findings that can be used for a system like the system 1200 of FIG 12 can be applied. The procedure 1400 of 14 includes all steps of method 1300 of 13 and additionally processing one or more of the sprites corresponding to the virtual point which may also be present and which conventionally would result in the perception of one or more sprites of the virtual image.

Method 1400 may be performed by any suitable processor. The processor may comprise, be included in, or be in communication with a hologram engine. The processor or the hologram module can be contained in a light module.

The processor may obtain or receive peripheral information about the system prior to performing the method. For example, it may obtain or receive information about the size of components such as the display device, information about the absolute and/or relative positions of various components and the viewer, information about the light source, and so on.

In some cases, the inventors have found that the ghost pixels are caused by that the light from the corresponding virtual point passes through a part of the display device other than the "primary contributing area" through which the main ray of the main image passes. In the previous figures, such parts of the display device are referred to as "secondary contributing areas". The light that creates one or more ghost pixels may be referred to as one or more "ghost rays." The light rays that create the ghost image may undergo a different number of turns within the waveguide than the light rays corresponding to the main image in order to also pass through the narrow pupil of the viewer's eye and meet the retina. Thus, if it is determined that the principal ray corresponding to the main image undergoes diversions within the waveguide "B", it can be determined that the light corresponding to a ghost undergoes diversions "B + ΔB", where ΔB is negative or positive may be an integer, typically a single digit number, for example in the range -5 to +5.

According to the improved method 1400 from 14 after the fourth step 1308 of the method 1300 of 13 , in which the position of the main image point on the viewing plane is defined - for example its coordinates ( _x-sensor , _y-sensor , _z-sensor ) -, the subsequent steps of method 13 from 13 be continued and additionally, for example in parallel or at a later point in time, a further series of steps as follows are carried out for at least one value of DB. In summary, the improved method 1400 of 14 , how many bounces 'B + ΔB' a ghost ray would have traversed from the coordinates [ _xvirtual , _yvirtual , _zvirtual ] of the virtual point to form a ghost pixel in the viewing plane. Then the improved method 1400 determines a shifted (or changed) location of the virtual point from which the light could propagate and suffer "B + ΔB" bounces within the waveguide to go to the main pixel in the viewing plane, rather than a separate one to form a ghost dot. A location on the LCOS through which a light beam travels from the translated virtual point location to the main pixel can then be identified and appropriately encoded with a hologram. In this way, one or more additional areas of the LCOS (other than the primary contribution area) can be encoded with hologram values to contribute to the main image while avoiding ghosting.

• In einem ersten weiteren Schritt 1402 werden Lichtstrahlen vom Hauptbildpunkt (_xsensor, _ysensor, _zsensor) zum virtuellen Bild zurückverfolgt, allerdings für Lichtstrahlen, die im Wellenleiter „B + ΔB“-Rückpralle/Reflexionen (statt B-Rückpralle) durchlaufen.

In detail, the improved method 1400 looks like this:

• In a first further step 1402, light rays from the main pixel ( _xsensor , _ysensor , _zsensor ) are traced back to the virtual image, but for light rays that pass through "B + ΔB" bounces/reflections (instead of B bounces) in the waveguide.

In a second further step 1404 the location - eg the coordinates [ _xvirtual (ΔB), _yvirtual (ΔB), _zvirtual (ΔB)] - is determined (eg, as a result of the ray tracing performed in the first further step 1402), a secondary virtual point of the virtual image that would be mapped onto the main pixel [ _xsensor , _ysensor , _zsensor ] - i.e., which would propagate light propagating through the display device, waveguide and entrance aperture to coincide with the viewing plane at location [ _xsensor , _ysensor , _zsensor ] to coincide - if the light “B + ΔB” were to go through reflections. The term "secondary virtual point" is used herein as an abbreviation for a secondary (ie, moved or changed) location of the (primary) virtual point. That is, the inventors realized that when the location of the virtual point is shifted to the location of the "secondary virtual point" [ _xvirtual (ΔB), _yvirtual (ΔB), _zvirtual (ΔB)], each light from the "secondary virtual point ', which is subject to 'B + ΔB' reflections in the waveguide, would contribute to the main image in the viewing plane.

In summary, a third further step 1406 comprises determining the coordinates [x _LCOS (B+ΔB), y _LCOS (B+ΔB), z _LCOS ] of a principal ray at the display device for the light propagation of [ _xvirtual (ΔB) _{p yvirtual} (ΔB) , _zvirtual ] to the viewing plane for B+DB impingements within the waveguide. In some cases, _zvirtual can be adjusted to account for the different path length through the waveguide (i.e. due to the different number of bounces. This main beam can be referred to as the "secondary main beam".

More specifically, in the third further step 1406, a point is identified on the display device where the "secondary principal ray" would pass from the secondary virtual point to the principal pixel [ _xsensor , _ysensor , _zsensor ] at B + ΔB in the waveguide via that point. This point on the display device has the coordinates [x _LCOS (B+ΔB), y _LCOS (B+ΔB), z _LCOS ].

In a fourth additional step 1408, the point [x _LCOS (B+ΔB), y _LCOS (B+ΔB), z _LCOS ] is assigned a radius or other suitable indicator of the extent or size of a region connected thereto. The area associated with the [x _LCOS (B+ΔB), y _LCOS (B+ΔB), z _LCOS ] point is referred to herein as the “extra area”. net because it propagates light that contributes to the main pixel in the viewing plane, but only if that light emanates from a shifted or changed location of the (primary) virtual point, ie, [ _xvirtual (ΔB), _yvirtual (ΔB), _zvirtual ] and not [ _xvirtual , _yvirtual , _zvirtual ] as determined in the second further step 1404 .

The fourth further step 1408 is similar to the sixth step 1312. In particular, the fourth further step 1408 includes identifying a region of the display device that coincides with the intersection point of the display device [x _LCOS (B+ΔB), y _LCOS (B+ΔB), z _LCOS (B)] is connected. The face of the display device can be geometrically centered on this point [x _LCOS (B+ΔB), y _LCOS (B+ΔB), z _LCOS (B)]. The area can be a circle or an ellipse, for example, but other, more complex shapes are also conceivable. If the area is a regular shape such as a circle or an ellipse, the radius of the area can be specified, e.g. B. depending on the f-number of the lens of the viewing system. The surface is referred to here as "additional contributing surface" because it propagates light that contributes to the virtual image when a corresponding hologram is computed based on the shifted or changed location of the (primary) virtual point.

A fifth further step 1410 is similar to the seventh step 1314. The fifth further step 1410 is optional. In the fifth further step 1410, a hologram component for the additional contributing region is determined based on the changed position of the (primary) virtual point [ _xvirtual (ΔB), _yvirtual (ΔB), _zvirtual ]. Specifically, the light parameters for the additional contribution area are determined. The light parameters can be amplitude and/or phase for each pixel of the additional area. For example, light amplitude and phase for each pixel within the additional area can be determined based on the propagation of the light from the various virtual points [ _xvirtual (ΔB), _yvirtual (ΔB), _zvirtual ] to the additional area using a point cloud method known to those skilled in the art become. The hologram component for the respective virtual point [ _xvirtueii (ΔB), _yvirtual (ΔB), _zvirtual ] can be stored and combined with the hologram component for the other virtual points as part of the iteration described in the following paragraph to obtain a complete hologram for the entire virtual to create image.

This required modulation of light, which is output by the display device in relation to a single virtual point, can be referred to as the "hologram component" for that virtual point. The hologram component may be stored by the processor at a later iteration of method 1300 for one or more other virtual points within the virtual image to be created.

The steps 1402 through 1410 of the further improved method 1400 of FIG 14 along with steps 1302 through 1314 of method 1300 of 13 be repeated for each virtual point within a virtual image to be created. Once the modulation behavior and corresponding hologram components have been determined for each virtual point, the hologram components can be added to produce a resulting modulation behavior for each pixel of the display device. This resulting modulation behavior presents a diffractive structure or hologram for the virtual image which, when displayed and illuminated on the display device within the viewing system, results in only the formation of a main image and no ghost image formation. The main image obtained when performing the improved method 1400 of 14 would result may be brighter than a corresponding main image resulting from method 1300 of 13 results.

The processor can output data corresponding to the hologram in any suitable manner. The hologram can be encoded on the display device. This adjusts the display device to modulate the light so that the virtual image can be seen by the viewer at the desired distance without ghosting.

The method 1400 can be performed substantially simultaneously (or in very rapid succession) for each of a plurality of virtual points within a virtual image, such that an appropriate hologram for the entire virtual image can be derived and encoded on the display device very quickly, viz for a given viewing setting and for certain numerical measurements and constraints. If anything changes that could affect the identification and/or the required adjustment of the display device, the procedure can be performed again. The processor may be configured to repeat the method in a timed loop and/or in response to a signal indicating that a change has occurred and/or when the content or identity of the required virtual image changes performs. The processor may include or be in communication with memory to store previously computed data. For example, a lookup table or a other storage means may be provided indicating the active area(s) of the display device for a particular virtual image or virtual point under a particular set of measurements and/or constraints.

The method 1400 can be executed (or repeated) very quickly to display a series of different virtual images in rapid succession and/or to accurately respond to changing conditions such as user movement. Although in the system of 12 only one eye is shown, the method 1400 can be configured to consider both eyes of the viewer. Although some of the above descriptions refer to an aperture size, it will be understood that a pupil (and most other scope apertures) is two-dimensional and can change size in either of these two dimensions. The method 1400 can be configured to take into account the two-dimensional size of the aperture and changes therein.

Hologram calculation - example 2

The in the 13 and 14 The methods illustrated include methods for computing point cloud holograms, but the inventors' discoveries extend to computing holograms by any suitable method, including Fresnel and Fourier hologram computation methods. In other words, the present inventors have recognized that a hologram can be computed and displayed on a relatively small display device located at a relatively large distance from the viewer in one of several possible ways, with a waveguide suitably between the display device and the viewer is arranged so that the viewer sees a virtual image at a finite distance in front of the display device without ghosting. This can also be done by projecting the light of the hologram directly onto the viewer's eye without creating an intermediate holographic reconstruction.

For example, the inventors have developed a method for calculating holograms for the in 15 developed optical system shown. It is important that the display device is relatively small and the projection distance is relatively large. The hologram is projected directly onto the viewing system and the process can be performed in real time. As with the in the 6A ff. Arrangements shown require the relatively small size of the display device and the relatively large projection distance a pupil dilator. The method takes into account the different paths through the pupil dilator and the size and shape of the entrance aperture(s) of the viewing system. In addition, the method allows the image content to appear at different distances from the viewing system and/or at a plurality of distances, possibly also simultaneously - e.g. B. with a hologram. The method allows the image content to appear downstream of the display device and upstream of the display device, optionally simultaneously - e.g. B. using a hologram.

15 Figure 15 shows a spatial light modulator 1501 capable of displaying a hologram of an image. In this embodiment, the spatial light modulator 1501 is a liquid crystal-on-silicon device arranged to modulate the phase of the received light. Spatial light modulator 1501 is illuminated with at least partially coherent light from a light source (not shown). The light source can be a laser diode. The spatial light modulator 1501 outputs light spatially modulated in accordance with the display hologram. 15 FIG. 15 shows an exemplary light beam 1502 of the spatially modulated light. It can be seen that the spatial light modulator 1501 typically outputs multiple beams of spatially modulated light. The spatially modulated light is received by a pupil expander 1503 . The pupil expander 1503 is inclined with respect to the plane of the display device 1501 . The pupil expander 1503 therefore receives light with an abnormal angle of incidence. The angle of incidence (the angle that the optical axis makes with the pupil dilator) can be less than 25 degrees, for example 10 to 20 degrees. The pupil expander includes an entrance surface 1503a receiving the spatially modulated light and an exit surface 703b. The entrance surface 1503a and the exit surface 1503b are substantially parallel and elongated in the direction of pupillary dilation. The input surface 1503a includes at least a portion that is substantially fully reflective (e.g., R=1). The output surface 1503b includes at least a portion that is highly reflective but partially transmissive (e.g., R=0.9 and T=0.1). The reflective surfaces are arranged so that spatially modulated light bounces back and forth between them and light is emitted at a plurality of points along the output surface 1503b, as discussed above with reference to the waveguide 608 in FIG 6A described. In this embodiment, the pupil expander is essentially elongate. The pupil expander provides pupil dilation in one direction - longitudinally - but the present disclosure can be expanded to include the presence of a second pupil expander arranged to dilate the pupil in an orthogonal direction.

15 Figure 12 shows how light ray 1502 was effectively replicated twice to form three propagation paths 1505, each connected at a different distance: Z ₀ , Z ₁ and Z ₂ . The shortest propagation path corresponds to Z ₀ and in this example the light that has passed through the waveguide without internal reflections. The middle of the three propagation paths shown corresponds to Z ₁ and two internal reflections in the pupil expander (one on each surface). The longest propagation path corresponds to Z ₂ and four internal reflections in the pupillary dilation (two on each surface). Planes x ₀ , x ₁ and x ₂ show the spatial extent of the light field associated with each of the three propagation paths Z ₀ , Z ₁ and Z ₂ , respectively. More precisely shows 15 , how the three planes x ₀ , x ₁ and x ₂ are offset from each other in the x-direction

15 15 further shows a viewing system 1513 having an entrance pupil 1507, a lens 1509, and a light sensor 1511. In embodiments, the viewing system 1513 is a human eye and the light sensor 1511 is the retina of the eye. 15 shows how only part of the light field associated with each propagation path passes through the entrance 1507. 15 15 shows how the light ray associated with the center of the propagation path at the middle distance passes through the center of the entrance pupil 1507. FIG. However, the light beam associated with the center of the light field of the shortest propagation path is blocked by an upper part of the opening 1507, for example. However, other light rays associated with the light field having the shortest propagation path can pass through the aperture 1507 . The light beam associated with the center of the light field of the longest propagation path is blocked by a lower part of the aperture 1507 . However, other light rays associated with the longest propagation path light field may also pass through the aperture 15807 .

The light incident through the opening 1507 is focused by the lens 1509 onto the light sensor 1511 . The plane of the light sensor 1511 is essentially parallel to the plane of the display device 1501 and is therefore also inclined with respect to the longitudinal dimension of the pupil dilation 1503 .

15 FIG. 15 shows, by way of example, three possible light propagation paths of a single beam 1502 of spatially modulated light. The present disclosure is not limited by the number of propagation paths. As those skilled in the art will appreciate from the following description, the method can be extended to accommodate any number of light propagation paths. Likewise, it is not necessary for the pupil expander to be tilted relative to the display and sensor plane. Using the procedure referred to below 16 , an appropriate hologram can be calculated to ensure that the spatially modulated light reaches the viewer's eye correctly for a range of different pupil expander settings and for any number of light reflections within the pupil expander and hence for any number of light propagation paths . Importantly, it takes into account the size and shape of the entrance aperture of a viewing system so that all the light required from an image reaches the viewer.

16 Figure 12 is a flow chart showing the steps of the method. The process is similar to a Gerchberg-Saxton-type algorithm that uses mathematical transformations between the image plane and the hologram to converge on a phase hologram corresponding to the image, which can be a virtual image, at a finite distance in front of the spatial light modulator 1501 can be formed. The amplitude component of the light field is modified or limited after each propagation into the image plane or hologram plane, but the phase component is preserved.

A zeroth stage of the method includes steps 1602 and 1604. The zeroth stage involves forming a zeroth complex light field. Step 1602 provides a random phase seed that forms the phase component of the zeroth complex light field. Step 1604 provides the amplitude component of the zeroth complex light field. The amplitude component can be a unit or an amplitude distribution representative of the light from a light source used to reconstruct the image from the hologram.

In step 1606, the zeroth complex light field is propagated from the spatial light modulator 1501 (ie, from the hologram plane) to the entrance pupil 1507 of the viewing system 713 (more specifically, to the plane containing the entrance pupil 1507 of the viewing system 713) according to Fresnel. Again, this embodiment refers to Fresnel propagation as just one example of a number of different mathematical transformations that can be used without departing from the spirit or scope of this disclosure. Step 1606 is performed for each number of bounces or internal reflections provided by the pupil dilation 1503 to form a complex field of light with respect to each light propagation path. In step 1606, the lateral position of the complex light field in the x-direction in the plane of the entrance pupil 1507 and the Phase shifts at each reflection within the pupil dilator 1503 are taken into account. The various complex light fields can e.g. B. be combined by addition. The first stage further includes step 1608 in which the combined complex light field is cropped according to the size and shape of the entrance pupil 1507 to form the first complex light field at the entrance pupil 1507 .

A second stage of the method includes steps 1610 and 1612. In step 1610, a second complex light field is determined by propagating the first complex light field from the entrance pupil through lens 1509 and into the light sensor 711 plane. Step 1612 involves changing the amplitude component of the complex light field arriving at the light sensor 711 . More specifically, step 1612 includes replacing the amplitude component of the complex light field with the amplitude component of the target image or an amplitude component based on that of the target image, such as a weighted version of the amplitude component of the target image. The position of the lens 1509 used in propagation determines the image distance, i. H. the space in which the image content will appear. In some embodiments, the image is a virtual image and this distance may be referred to as the virtual image distance "VID".

Advantageously, the method disclosed herein allows image content to be generated at a variety of different image spacings - e.g. B. multiple VIDs - using the same hologram. The inventors have found that this can be achieved by repeating the second stage for each image distance by considering different positions of the lens 1509 in the z-direction. The complex light fields determined in this way for each image distance can e.g. B. be combined by addition.

A third stage of the method includes the step 1614 in which the second complex light field is propagated via the lens 1509 back to the entrance pupil 1507 . This can be called reverse propagation to make it clear that the light is traveling in the opposite z-direction. In some embodiments, the reverse propagation is a mathematical inverse of the corresponding "forward" propagation. The third stage also includes cropping the propagated light field according to the size and shape of the entrance pupil 1507 to form the third complex light field.

A fourth stage includes steps 1616 and 1618. In step 1616, the light is propagated back into the plane of the spatial light modulator 1502 via the multiple light propagation paths of the pupil expander, as described above in relation to the first stage - but of course in the opposite light direction (i.e. a "reverse" propagation). Step 1618 includes cropping the propagated light field according to the size and position of the active/pixel area of the display device. The number of complex values of each complex light field can be equal to or less than the number of pixels of the display device.

Step 1620 includes extracting the hologram from the fourth complex light field. The hologram can include the phase values of the fourth complex light field, in which case the hologram can be referred to as a kinoform. The process can also start in the image plane (ie in the third stage). In accordance with this disclosure, at least one iteration of each stage is required. The 17A and 17B describe the according to this procedure and according to the procedures of 13 and 14 manufactured hologram.

Channeling hologram

The inventors have found that a hologram (or a "kinoform" or a "diffractive structure") calculated according to the present disclosure, regardless of the method by which it is calculated, has unique properties that cannot be achieved with conventional methods in the art hologram calculation are not observable or reachable.

In summary, a hologram computed in accordance with the present disclosure enables a display device, such as an LCOS, on which it is displayed and illuminated to emit channels of spatially modulated light, each channel corresponding to a different portion of the corresponding image. This unique channeling allows the display device, in conjunction with an appropriate pupil dilatation, such as e.g. a waveguide, to allow a viewer to accurately see the entire image through the relatively small opening of his eye, even when the viewing distance is relatively long and the display device is relatively small, and without having to move his eye. For example, a virtual image located at a limited distance in front of the display device can be viewed (correctly and completely) at a relatively large distance, despite the fact that both the opening of the viewer's eye and the display device on which the hologram is displayed , are relatively small. This was not previously possible with either conventional holography or non-holographic techniques.

In accordance with one aspect of this disclosure, the inventors found that when the hologram is computed using a "point cloud" method as described above, the light from each virtual pixel is constrained according to a different, corresponding primary contributing area of the display device. The inventors have further recognized that this means that the light from different parts of the virtual image (ie from different virtual pixels) follows different optical paths through the system. Similarly, in accordance with one aspect of this disclosure, the inventors have found that when the hologram is computed using Fresnel propagation, such as e.g. B. through the in 16 In the methods shown, spatially modulated (ie "holographic") light corresponding to different respective parts of the image follows different respective optical paths. Thus, the inventors realized that the hologram (regardless of how it is computed) can be employed to direct each of these optical paths towards the viewer's eye simultaneously, allowing the viewer to receive all of the holographic light that is brain is required to reconstruct the entire image without moving his eye(s) or making other physical changes. As shown in the detailed examples above, a waveguide or other pupil dilation can be used in conjunction with a display device that displays the computed hologram(s) to achieve this.

In one in the 17A and 17B In the illustrated embodiment, the inventors configured an optical system to display a virtual image that includes a plurality of discrete virtual image components or regions to aid in understanding the unique properties of holograms as disclosed herein. However, the present disclosure is equally applicable to the computation and display of holograms corresponding to images with continuous (ie non-discrete) image content and/or to holograms of images with any number/size/pitch of discrete image parts. In the 17A and 17B Put simply, the virtual image comprises (i) a plurality of discrete virtual image components or regions, and (ii) the light of each virtual image component is associated with a different number of bounces/reflections within the waveguide 1708. However, in some other embodiments, it is possible for the light of two or more discrete virtual image components within the waveguide to experience the same number of bounces.

17A Figure 1752 shows an image 1752 for projection comprising eight discrete image areas/components, V1 through V8. 17A shows eight image components by way of example only; the image 1752 can be broken down into any number of components. 17A 17 also shows the encoded light pattern (ie, the pattern of holographic light) 1754 that is formed when the hologram (computed as disclosed herein) is appropriately displayed and illuminated. The encoded light pattern 1754 can reconstruct the image 1752 when viewed through the lens of a suitable viewing system, e.g. B. the eye (eyes) of the viewer is transformed. The encoded light pattern 1754 includes first through eighth components or channels, H1 through H8, corresponding to first through eighth image components/regions, V1 through V8. The hologram can thus be characterized by the channeling of holographic light that it performs. This channeling of the light is due to the way of calculation and is in 17B shown. Specifically, according to this disclosure, the hologram directs the holographic light into a plurality of discrete channels, which may be formed as discrete regions in a plane. The discrete areas are discs in the example shown, but other shapes are also conceivable. As described above, the hologram is calculated (e.g., cropped) specifically with regard to the size/shape of the light field at the display device and/or the size/shape of the light field at the viewing aperture(s). Therefore, the size and shape of the optimal disk may be related to the size and shape of the viewing system's entrance pupil.

It should be apparent from the present disclosure that this type of hologram can be calculated using any method, and a key finding of the inventors is that this type of hologram can be used to provide a relatively large field of view with a relatively small display device. The hologram behavior disclosed here is synergistic with a hologram replicator such as a pupil dilator. The holographic system described here is particularly synergistic with head-up displays.

The holographic light channels emitted by the hologram effectively decompose the image content (the image to be holographically reconstructed by the viewer) by angles. This can be compared with the optical arrangement of 4 as understood above, in which light rays come from a plurality of discrete locations on a real image 401 at a plurality of discrete corresponding angles to the aperture (or to the viewing window) 402, but the light from only one of these beams can pass through the viewer's eye at any given eye position. A hologram, computed as described herein and displayed by a suitable display device, can form a holographically reconstructed virtual image to mimic the presence of that image 401 (or any image/object) at a desired image distance. A notable advantage over the optical system of 4 However, and over conventional holographic systems is that the hologram computed as described herein allows the entire image to be seen or perceived by the viewer even when the display device is relatively small and when an entrance aperture of the viewing system, such as e.g. the viewer's eye, is relatively small and when the viewing distance is relatively large. In other words, and as a non-limiting example, the hologram would allow all five in 4 shown light beams reach the viewer at the same time and thus completely form the desired virtual image.

Importantly, such a hologram, when appropriately displayed and illuminated, causes the display device to emit channels of holographic light, each channel of holographic light corresponding to an angle (or in some cases a bundle of angles) at which light would arrive at the display device from a corresponding part of the desired image/object. It can thus be said that the channels of holographic light each correspond to different angular sections of the image content. This is not the case with conventional holograms. In contrast to the unmodulated light of a real image/object or the spatially modulated light of a conventional hologram, the holographic light channels disclosed herein are specifically configured to be guided through a suitable waveguide or other pupil dilator located between the display device and the viewer to ensure that each of the channels - and hence the holographic light corresponding to each (i.e. each) part of the image - can be received simultaneously by the viewer. Also, each channel can only be received once, at least in some embodiments.

17C shows an improved viewing system 1700 that uses the methods shown in FIGS 17A and 17B matches the detections shown. The procedure 1300 from 13 or the procedure 1400 of 14 or the procedure of 16 or any other suitable method can be used to calculate the hologram according to the 17A until 17C scheme shown can be applied.

Viewing system 1700 includes a display device, which in this arrangement includes an LCOS 1702 . The LCOS 1702 is arranged to display a modulation pattern (or "diffraction pattern") that includes the hologram and projects light that has been holographically encoded onto an eye 1705 that has a pupil that serves as an aperture 1704, a lens 1709 and a retina (not shown) serving as the viewing plane. There is a light source (not shown) arranged to illuminate the LCOS 1702. The light source can be a laser diode, for example. The hologram is configured so that the entire hologram can be illuminated by a single beam of light (or a single bundle of beams of light). It is not necessary for multiple light sources or, for example, a multitude of light beams, each with different wavelengths, to illuminate the hologram for it to function as described herein.

The lens 1709 of the eye 1705 performs hologram to image conversion. So there is no holographic reconstruction of the image between the LCOS and the eye 1705.

The viewing system 1700 further includes a waveguide 1708 disposed between the LCOS 1702 and the eye 1705 . The projection distance in 17C can be relatively large. However, as described in the previous figures, the presence of the waveguide 1708 allows the entire angular content of the LCOS 1702 to be received by the eye 1705, even at this relatively large projection distance. This is because the waveguide 1708 acts as a pupil dilator as described above.

In this arrangement, once the LCOS 1702 has been encoded according to the methods disclosed herein, the waveguide 1708 can also be oriented at an angle to the LCOS 1702 to establish a unique relationship between the light from the LCOS 1702 and the virtual image that the viewer will perceive . The size, location and position of the waveguide 1708 are configured so that the light from each holographic channel - and therefore the light from every part of the virtual image - enters the waveguide 1708 and is guided along its longitudinal axis, passing between the substantially planar Surfaces of the waveguide 1708 bounces off. Each time the light reaches the second flat surface (closest to the eye 1705), it becomes a part of the light is transmitted and another part is reflected.

17C Figure 12 shows a total of nine "bounce" points, B0 through B8, along the length of waveguide 1702. The reader will note that the center of image 1752 remains blank. 17C shows the zeroth through ninth light "bounce" or reflection points, B0 through B8, within the waveguide. Although the light relating to all points of the image (V1-V8) - ie, light from each of the eight holographic light channels H1 to H8 - is transmitted out of the waveguide at each "bounce" off the second planar surface of the waveguide 1708, only the light from an angular part of the image (e.g. light from one of the channels H1 to H8 corresponding to a certain image part V1 to V8) has a trajectory that allows it to focus the eye 1705 from each respective "bounce" reach point B0 to B8. Furthermore, in this embodiment, light from a different channel - and hence light from a different angular portion of the image (V1 through V8) - reaches the eye 1705 from each respective "bounce" point. 17C shows how the light of all different holographic light channels is emitted at each "bounce" point (represented by a multitude of short arrows at each transmission point), but then only shows the optical path of each channel to the eye 1705 corresponding to a unique respective part of the image (ie, a unique respective angle image content) actually reaching the eye 1705 from that bounce point. The channel whose optical path is indicated as reaching the eye for each bounce point is the channel that will contribute a corresponding part of the virtual image from the corresponding part of the waveguide. For example, the light transmitted by waveguide 1708 is simply refracted at the zero bounce point, B0, and experiences no reflections therein. The light from the eighth holographic channel, H8, reaches the eye from the zeroth bounce, B0. At the next bounce B1, the light transmitted by the waveguide 1702 undergoes a bounce therein before transmission. The light from the seventh hologram, H7, reaches the eye on the next bounce B1. This continues in sequence until the light transmitted by the waveguide 1708 on the last bounce B8 has gone through eight bounces before being transmitted and the Reaches eye 1705 and includes light encoded according to first hologram H1. With this arrangement, the light from each channel reaches the viewer simultaneously, each from a plurality of different bounce points on the waveguide. In this way, the viewer receives the holographic light corresponding to the entire virtual image at the same time without moving his eye or making any other changes, although his eye and the display device are relatively small and the viewing distance is relatively large.

In the in the 17A until 17C In the example shown, the light of only one image area reaches the eye from each rebound point. Therefore, a spatial correlation is established between the regions of the virtual image and the associated point of reflection on the waveguide when determining the hologram as described herein. In some other examples, there may be relatively small overlaps such that a portion of the image originates from two adjacent transmission points and is thus contained in two adjacent light sheets propagating from the waveguide towards the viewing plane.

Thus, the findings made by the inventors and the methods and arrangements disclosed herein may make it possible to generate a diffractive pattern (or light modulation pattern) comprising a hologram which, when displayed on an LCOS or other suitable display device, make it possible that the spatially modulated light is effectively emitted in a plurality of "slices" or channels of holographic light, each corresponding to (more specifically, encoded) a different part of the corresponding virtual image.

Therefore, improved methods and arrangements are disclosed herein that allow holograms to be computed and displayed on a suitable display device such that a viewer can see clear images when the display device is illuminated by a suitable light source. The images that the viewer sees may be ghost-free and, in at least some embodiments, may be brightened by the contribution of light that would normally have contributed to a ghost and instead contribute to the single main image. In addition, they allow the viewer to see an image, e.g. a virtual image, is seen at a finite distance from the display (rather than infinity), even though the display and the viewer's viewing aperture(s) (i.e., the eyes) are relatively small and the viewing distance is relatively large.

The improved methods and arrangements disclosed herein can be performed in real time and, for example, repeated very quickly to account for changes in the location/position of the viewing port. They can be implemented for more than one viewing port, for example two eyes. They can be repeated, for example on a very rapid basis, to enable a variety of different holograms to be displayed and thus viewed a plurality of different corresponding images, in succession and/or in a sequence, series, pattern or loop.

The improved methods and arrangements described herein can be used in a variety of different applications and vision systems. For example, they can be implemented in a head-up display (HUD). An improvement over many conventional HUDs that generate virtual images in the infinite range is that the improved methods and arrangements disclosed herein can be implemented to generate virtual images at finite image intervals selected and adjusted by an appropriate controller can be achieved while at the same time avoiding ghost images.

Although virtual images are discussed here, in which the eye must convert the received modulated light in order to produce a perceived image, the improved methods and arrangements disclosed herein can also be applied to real images.

Additional characteristics

The exemplary embodiments relate to an electrically activated LCOS spatial light modulator, to give just one example. The teachings of the present disclosure can also be implemented on any other spatial light modulator capable of displaying a computer generated hologram in accordance with the present disclosure, such as. B. electrically activated SLMs, optically activated SLMs, digital micromirror devices or microelectromechanical devices.

In some cases the light source is a laser, e.g. B. a laser diode.

The system of the present disclosure may be used to provide an enhanced head-up display (HUD) or head-mounted display. In some embodiments, a vehicle is provided that includes the holographic projection system installed in the vehicle to provide a HUD. The vehicle can be a motor vehicle such. B. act a car, truck, van, truck, motorcycle, train, plane, boat or ship.

The quality of the holographic reconstruction can be affected by what is known as the zero-order problem, which arises from the diffractive nature of using a pixelated spatial light modulator. Such zero-order light can be considered "noise" and includes, for example, specularly reflected light and other unwanted light from the SLM.

In some embodiments, only the primary playfield is used and the system includes physical blocks, such as e.g. B. Baffles arranged to restrict the propagation of the higher order display fields through the system.

In some cases, the holographic reconstruction is done in color. In some embodiments, an approach known as spatially separated colors ("SSC") is used for color holographic reconstruction. In other embodiments, an approach known as Frame Sequential Color (FSC) is used.

The SSC method uses three spatially separated arrays of light modulating pixels for the three single color holograms. An advantage of the SSC method is that the image can be very bright since all three holographic reconstructions can be created at the same time. However, if, for reasons of space, the three spatially separated arrays of light modulating pixels are provided on a common SLM, the quality of each single color image will be sub-optimal, since only a subset of the available light modulating pixels will be used for each color. Accordingly, a relatively low-resolution color image is produced.

With the FSC method, all the pixels of a common spatial light modulator can be used to sequentially display the three monochromatic holograms. The monochromatic reconstructions are swept through so rapidly (e.g., red, green, blue, red, green, blue, etc.) that a human viewer perceives a polychrome image from the integration of the three monochromatic images. An advantage of FSC is that the entire SLM is used for each color. This means that the quality of the three color images produced is optimal since all the pixels of the SLM are used for each of the color images. A disadvantage of the FSC method, however, is that the brightness of the composite color image is about a factor of 3 lower than that of the SSC method, since each monochromatic illumination event can only occur during a third of the image time. Overdriving the lasers or using more powerful lasers could possibly overcome this disadvantage, but this requires more energy and increases the cost and size of the system.

The examples describe the illumination of the SLM with visible light, but the Those skilled in the art will understand that the light sources and the SLM can also be used to e.g. B. to conduct infrared or ultraviolet light as disclosed herein. For example, techniques are known to those skilled in the art for converting infrared and ultraviolet light into visible light in order to make the information available to a user. For example, the present disclosure extends to the use of phosphors and/or quantum dot technology for this purpose.

In some embodiments, 2D holographic reconstructions are described by way of example only. In other embodiments, the holographic reconstruction is a 3D holographic reconstruction. That is, in some embodiments, each computer generated hologram forms a 3D holographic reconstruction.

The methods and processes described herein may be embodied on a computer-readable medium. The term "computer-readable medium" includes a medium adapted for the temporary or permanent storage of data, such as B. random access memory (RAM), read only memory (ROM), buffer memory, flash memory and cache memory. The term "computer-readable medium" also includes any medium, or combination of media, capable of storing instructions for execution by a machine such that the instructions, when executed by one or more processors, cause the machine to to carry out one or more of the methods described herein in whole or in part.

The term "computer-readable medium" also includes cloud-based storage systems. The term "computer-readable medium" includes, but is not limited to, one or more tangible and non-transitory data stores (e.g., data volumes) in the exemplary form of a solid-state memory chip, an optical disk, a magnetic disk, or any suitable combination thereof. In some embodiments, the execution instructions may be communicated via a carrier medium. Examples of such a carrier medium are a transient medium (e.g. a propagating signal conveying instructions).

It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope of the appended claims. The present disclosure includes all modifications and variations within the scope of the appended claims and their equivalents.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US10514658 [0052]
• GB2498170 [0114]
• GB2501112 [0114]

Claims (17)

Diffractive structure arranged to spatially modulate light that can be converted into an image by a viewing system, the diffractive structure being configured to direct light into a plurality of hologram channels, each hologram channel being a different part corresponds to the picture. Diffractive structure after claim 1 , which is arranged in such a way that the hologram channels propagate from the diffractive structure at different angles. Diffractive structure after claim 1 or 2 , each hologram channel comprising substantially spatially modulated light corresponding to a different part of the image. A diffractive structure as claimed in any preceding claim arranged to spatially modulate the phase of the light. A diffractive structure as claimed in any preceding claim arranged to direct light through a waveguide. Diffractive structure after claim 5 , wherein the waveguide is set up for pupil dilation. Diffractive structure according to one of Claims 1 until 6 , wherein the cross-sectional shape of the light pattern shapeable by each hologram channel corresponds substantially to the shape of an entrance aperture of the viewing system. Diffractive structure according to one of the preceding claims, wherein the hologram channels are spatially separated or at least partially spatially separated. System with the diffractive structure according to one of Claims 1 until 8th , a waveguide arranged to receive the spatially modulated light from the diffractive structure, and a viewing system arranged to receive the spatially modulated light via the waveguide. system after claim 9 , which is designed in such a way that the light of each hologram channel takes a different optical path from the diffractive structure to the viewing system. system after claim 10 , where the different optical paths involve a different number of reflections within the waveguide. system after claim 10 or 11 , where the different optical paths have different lengths. system after claim 10 , 11 or 12 , in which the various optical paths pass through the entrance aperture of the viewing system at different angles. system according to one of the Claims 10 until 13 , wherein the waveguide is arranged such that all hologram channels pass through the entrance aperture of the viewing system at each viewing position in a viewing plane. system after Claim 14 , in which the waveguide guides each hologram channel over only one optical path to the viewing system for each allowed viewing position. system according to one of the claims 9 until 15 , wherein at least two hologram channels from the plurality of hologram channels partially overlap at the entrance aperture of the viewing system. Diffractive structure or diffractive system according to one of the preceding claims, wherein the diffractive structure is a kinoform or a hologram.

Images